Are there "conditions" set upon prophecy, in order for the word to come to pass, or to happen according to what is stated within it? Below are a few examples of conditions. Isaiah 38:1 "In those days Hezekiah became ill and was at the point of death. The prophet Isaiah son of Amoz went to him and said, "This is what the Lord says:
Put your house in order, because you are going to die you will not recover. Hezekiah turned his face to the wall and prayed to the Lord, "Remember, O Lord, how I have walked before you faithfully and with wholehearted devotion and have done what is good in your eyes. And Hezekiah wept bitterly. Then the word of the Lord came to Isaiah: "Go and tell Hezekiah, "This is what the Lord, the god of your father David, says: I have heard your prayer and seen your tears; I will add fifteen years to your life. And I will deliver you and this city from the hand of the king of Assyria. I will defend this city."
(Hezekiah was added fifteen years to his life because he came to the Lord in sincerity of heart, and sought the Lord with all of his heart. The first word that Isaiah gave to him was conditional upon Hezekiah's heart condition before the Lord. )
What about Jonah 1:1-2 "The word of the Lord came to Jonah son of Amittai: "Go to the great city of Nineveh and preach against it, because its wickedness has come up before me." 3:1-2 "Then the word of the Lord came to Jonah a second time: "Go to the great city of Nineveh and proclaim to it the message I give you." Jonah 3:7-9 "By the decree of the king and his nobles: Do not let any man or beast, herd or flock, taste anything; do not let them eat or drink. But let man and beast be covered with sackcloth. Let everyone call urgently on God. Let them give up their evil ways and their violence. Who knows? God may yet relent and with compassion turn from his fierce anger so that we will not perish."
(When God saw what they did and how they turned from their evil ways, he had compassion and did not bring upon them the destruction he had threatened.")
There certainly are prophecies that are “set in stone” and will happen as God has declared them. However, prophecies spoken or written, to individuals or groups, are conditional based upon the person or group's actions.
One of the reasons that prophecy is conditional is that it is meant to build-up the person’s faith in God and in those who speak for Him. People who do not realize that prophecy is conditional may have their faith shaken if a particular prophecy does not come to pass or if they see a prophecy in the Bible that did not come to pass. Those operating under this premise might then declare that Jonah was a false prophet because his message to Nineveh didn’t happen according to how the prophecy was given. But we know that Jonah was a true prophet of God. If a particular prophecy is not fulfilled, we should examine the prophecy and the situation to see if the reason that it was not fulfilled had to do with a shift in the situation.
Are there examples of prophecies where they are not conditional? We need to look and see. I do know that when personal words are addressed to individuals, and say such things as, "Child, you will be a woman of wisdom, and many people will seek you out, and come to you, because of your great learning, and willingness to help them." (Obviously, this person would need to continue in prayer, reading the Bible, and stay in close communion with the Lord.) If they stopped doing these things, then they wouldn't be a person of wisdom.) Time becomes an issue also, I believe. Some prophetic words are conditional upon a time element. Perhaps someone is told that they will enter the mission field, and leave the U.S. Maybe there needs to be a time frame, for these things to occur, and there may be other factors at work here also.
What of the many prophecies of Christ dying on a cross, and being mocked, and his garments being given away as stated in Isaiah?
Isaiah 53:2 "He had no beauty or majesty to attract us to him, nothing in his appearance that we should desire him. He was despised and rejected by men, a man of sorrows, and familiar with suffering. Like one from whom men hide their faces he was despised, and we esteemed him not. Surely he took up our infirmities and carried our sorrows, yet we considered him stricken by God, smitten by him, and afflicted. But he was pierced for our transgressions, he was crushed for our iniquities; the punishment that brought us peace was upon him, and by his wounds we are healed. We all, like sheep, have gone astray, each of us has turned to his own way; and the Lord has laid on him the iniquity of us all."
(This isn't all of the chapter, but we get the basic message here.) This was being prophesied about 700 years before the birth of Christ. He needed to die on a cross for this to happen, he needed to carry out the plan that God had laid out for him to do in his ministry, and the plans which led up to his death on a cross. The prophecies of Christ were not "conditional, because he was obedient to the Father, and fulfilled the law and the prophets. (Matthew 3:15, 4:14, and 5:17,18)
(Were these things going to happen regardless of what could or might have happened? I can't answer that. This was God's plan for mankind and a provision for us in eternal life, and forgiveness of sins.)
There are many prophetic messages lately which speak of "the coming judgment" upon this nation, and upon our world. God has been warning us again and again, and has stayed his hand for the time being. However, I believe, as many others do, that judgment is beginning, and soon will come. Perhaps, in some ways, it has already begun. May we be found in "safe habitations."
We can still prevent this from happening to us as a nation, and a people. "If my people, who are called by my name, will humble themselves and pray and seek my face and turn from their wicked ways, then will I hear from heaven and will forgive their sin and will heal their land." (II Chron. 7:14) And, I would further say, that if we as a people would do these things, then God would not do the things he has prophesied that He would do upon our nation. Then the prophetic word becomes "conditional" upon us, turning from our sins, and going in another direction. If we continue in our present course, then the inevitable becomes true, and the word comes to pass as prophesied.
In the book of Jeremiah, God reveals the conditional nature of prophecy, and He compared His working with people with a potter working with clay. The following selection from the text, would illustrate some of these aspects of conditionality.
(1) This is the word that came to Jeremiah from the LORD:
(2) “Go down to the potter’s house, and there I will give you my message.”
(3) So I went down to the potter’s house, and I saw him working at the wheel.
(4) But the pot he was shaping from the clay was marred in his hands; so the potter formed it into another pot, shaping it as seemed best to him.
(5) Then the word of the LORD came to me:
(6) “O house of Israel, can I not do with you as this potter does?” declares the LORD. “Like clay in the hand of the potter, so are you in my hand, O house of Israel.
(7) If at any time I announce that a nation or kingdom is to be uprooted, torn down and destroyed,
(8) and if that nation I warned repents of its evil, then I will relent and not inflict on it the disaster I had planned.
(9) And if at another time I announce that a nation or kingdom is to be built up and planted,
(10) and if it does evil in my sight and does not obey me, then I will reconsider the good I had intended to do for it.
(11) “Now therefore say to the people of Judah and those living in Jerusalem, ‘This is what the LORD says: Look! I am preparing a disaster for you and devising a plan against you. So turn from your evil ways, each one of you, and reform your ways and your actions.”
Some think that this portion of scripture points to the fact that God can do whatever He wants to do with His vessels. However, perhaps just the opposite is true, for the Lord has certain things in mind when He is shaping and creating a vessel, as is shown with the potter and the clay. The lump of clay was marred in appearance, and God’s hand needed to shape the clay into the image that it was created to be made into. But anyone who knows the nature of clay knows that the pliable appearance of the medium leaves one with the clay changing suddenly.
God gave Samuel the revelation that Saul would be king over Israel (1 Sam. 9:17). That revelation became prophecy when Samuel spoke it to Saul (1 Sam. 10:1). It was implied in the prophecy that Saul and his descendants would prevail over the Israel. There would have been no reason for the prophet to speak that; because that was simply the way kingdoms work: after the king dies, a descendant becomes king. However, Saul disobeyed the word of God and Samuel gave forth another prophecy that modified the original one. This one stated that Saul’s kingdom would not endure. The original prophecy was conditional upon Saul’s obedience to God.
1 Samuel 13:13 and 14
(13) “You [Saul] acted foolishly,” Samuel said. “You have not kept the command the LORD your God gave you; if you had, he would have established your kingdom over Israel for all time.
(14) But now your kingdom will not endure; the LORD has sought out a man after his own heart and appointed him leader of his people, because you have not kept the LORD’s command.”
One would have thought that Saul would have repented upon hearing this word from Samuel. Instead Saul continued in his disobedience.
1 Samuel 15:23, 26-28
(23) “For rebellion is like the sin of divination, and arrogance like the evil of idolatry. Because you have rejected the word of the LORD, he has rejected you as king.”
(26) But Samuel said to him [Saul], “I will not go back with you. You have rejected the word of the LORD, and the LORD has rejected you as king over Israel!”
(27) As Samuel turned to leave, Saul caught hold of the hem of his robe, and it tore.
(28) Samuel said to him, “The LORD has torn the kingdom of Israel from you today and has given it to one of your neighbors—to one better than you.”
Another good example of the conditional nature of prophecy can be seen in the life of Solomon. David wanted to build a temple for God, but God told him that Solomon would build the Temple, and also that “…I [God] will establish his kingdom.” The prophet Nathan foretold the establishment of Solomon’s kingdom.
2 Samuel 7:12 and 13
(12) When your days are over and you rest with your fathers, I will raise up your offspring to succeed you, who will come from your own body, and I will establish his kingdom.
(13) He is the one who will build a house for my Name, and I will establish the throne of his kingdom forever. 
These prophetic words seem very final. Solomon did much evil in his last years. God had said that a king was not to amass silver and gold, but Solomon received 666 talents (more than 49,000 pounds) of gold a year (Deut. 17:17; 1 Kings 10:14). God commanded that the king not amass horses or get horses from Egypt, but Solomon had thousands of horses, many of them from Egypt (Deut. 17:16; 1 Kings 10:26-29). God commanded that the king not have many wives, but Solomon had 700 wives and 300 concubines (Deut. 17:17; 1 Kings 11:3). God commanded that no Israelite marry a pagan woman, but Solomon married “Moabites, Ammonites, Edomites, Sidonians, and Hittites” (1 Kings 11:1 and 2). God commanded all Israel to stay away from idolatry (which was the first of the Ten Commandments), but Solomon worshipped Ashtoreth and Molech, among other pagan gods (1 Kings 11:5). Solomon “did evil” in the eyes of God (1 Kings 11:6), and after much sin, a different prophetic word came to him:
1 Kings 11:11
So the LORD said to Solomon, “Since this is your attitude and you have not kept my covenant and my decrees, which I commanded you, I will most certainly tear the kingdom away from you and give it to one of your subordinates.
Because Solomon disobeyed and turned from the commands of God, the kingdom, which God prophesied He would “establish,” was torn from David’s line. Only two tribes, Judah and Benjamin, became the kingdom of Judah. The ten northern tribes became their own kingdom, Israel.
ALL that is written in God's word must be fulfilled. The remaining parts of the book of Revelation, and some of Daniel, are not conditional, because again, they speak of God's appointed times and seasons. Again, though, man has a choice where he fits into this plan, and his actions will help fulfill a destiny of either being with Him forever, or without him in darkness. Acts 17:26,27
God has stated in His word that "Never again will I curse the ground because of man, even though every inclination of his heart is evil from childhood. And never again will I destroy all living creatures, as I have done.
"As long as the earth endures, seed time and harvest, cold and heat, summer and winter, day and night will never cease." Gen. 8:21-22
(This I believe, is an undeniable oath from God, and a promise.)
And God said, "This is the sign of the covenant I am making between me and you and every living creature with you, a covenant for all generations to come. I have set my rainbow in the clouds, and it will be the sign of the covenant between me and the earth. Whenever I bring clouds over the earth and the rainbow appears in the clouds, I will remember my covenant between me and you and all living creatures of every kind. Never again will the waters become a flood to destroy all life. Whenever the rainbow appears in the clouds, I will see it and remember the everlasting covenant between God and all living creatures of every kind on the earth." So God said to Noah, This is the sign of the covenant I have established between me and all life on the earth." Gen. 9:12-17
So, there are promises and oaths which God has stated in His word which will happen no matter what we might do. However, we can change what might be said prophetically (for us), when we turn from our evil ways, humble ourselves and pray, and turn again to Him. May we be found in "safe habitations," and not be counted with those who in their disobedience, will find their destinies fulfilled in the prophecies spoken now about the coming judgment, and in His word about what is going to come to pass.