I have a question, summarized pretty much by the title, did Jesus and/or God (depending on whether you accept the trinity doctrine) know that he would be crucified before being born a mortal man? I would appreciate answers backed up by scripture in order to answer this question.
Upvote for a good question.
I do not agree that an answer to your question involves mere opinion. The answer is yes, and the scriptural basis for that affirmative answer is both broad and deep.
While the assumption that Father, Son, and Holy Spirit are one in their divine nature is not required in order to understand how the Christ knew "well beforehand" of His ultimate death on a Roman cross in the first third of the first century in the Common Era, it is helpful.
First, we need to take the long (really long) view of things. If God exists outside time and space (both of which are His creations), then perhaps we are helped in our understanding of God's perspective regarding His Son by thinking of eternity as God's realm of existence (i.e., God exists in the eternal present). As such, eternity neither looks forward nor backward. A decision God makes in eternity may seem to finite human beings to be "worked out in time," but from God's perspective that "working out" is in a sense a fait accompli. God's plan for the ages is unalterable, and while it becomes evident to finite human beings in space and time, to God it is as good as accomplished. (The unalterability of God's plan diminishes neither His creatures' accountability nor their responsibility to do the right thing. Doing the wrong thing, however, cannot change the outcome of God's "big picture," since God has no Plan B, only Plan A. According to His plan, therefore, both God and good will triumph in the end. Handel's Messiah expresses this thought very well: "The kingdom of this world has become the kingdom of our Lord and of His Christ; and He shall reign forever and ever"--from Revelation 11:15.)
This perspective does not diminish one whit the significance of the great stoop Jesus took in becoming a flesh-and-blood human being (what theologians call His self-emptying, as in the Greek word kenosis, as found in Philippians 2:7), nor does it diminish the significance, not to mention the pain and suffering, of what Jesus accomplished not only through His life of continuous servanthood and obedience to the Father's will, but also through His death on a Roman cross, just outside Jerusalem at a place called Golgotha (Matthew 27:33 NAS; Mark 15:22 NAS; John 19:17 NAS).
A pivotal passage in this regard is 1 Peter 1:17-21, where we read (in excerpts):
" . . . you were not redeemed [i.e., set free from the penalty of sin, which is death] with perishable things like silver or gold . . . but with precious blood, as of a lamb unblemished and spotless, the blood of Christ. For He was foreknown before the foundation of the world, but has appeared in these last times for the sake of you, who through Him are believers in God, who raised Him from the dead . . .."
You see, the lamb (or the Lamb of God, who bears away the sin of the world, as in John 1:29 & 36) was offered up in sacrifice from eternity, according to God's
" . . . purpose, who works all things after the counsel of His will" (Ephesians 1:11).
In other words, the entrance of God's Son, the Messiah, into space and time, as well as His becoming the perfect sacrifice for sin at the cross, was all planned in the eternal counsels of God, but was revealed to us in the "fullness of time" (i.e., at the time of God's appointment; see Galatians 4:4).
And second, throughout the three-plus years of His public ministry, over and over again Jesus predicted His death. At various times He referred to it as His
- baptism (Mark 10:38 & 39; Luke 12:50)
- cup (ditto, plus Matthew 20:22 & 23; 26:39; Luke 22:42; John 18:11)
- being killed (the implication is that He would be killed by crucifixion; Matthew 17:23; Mark 9:31)
- being lifted up as the Son of Man (John 3:14 & 15)
In conclusion, the crucifixion of Jesus was planned by God in eternity "past," and it will become the song of the ages in eternity "future." In the Revelation of Jesus Christ we read:
"And they sang the song of Moses, the bond-servant of God, and the song of the Lamb, saying, " Great and marvelous are Your works, O Lord God, the Almighty; Righteous and true are Your ways, King of the nations! (Revelation 15:3 NAS)
Notice the two songs: Moses' song and the Lamb's song. The former celebrates God's earlier revelation of His will and word through the Law of Moses (or the Law given to Moses by God), and the latter celebrates the eternally efficacious sacrifice of Christ the Lamb, whose work of redemption at the cross was, in the mind of God,
". . . finished from the foundation of the world" (Hebrews 4:3).
Yes, God not only knew Jesus would die, but planned that it would happen:
For you know that God paid a ransom to save you from the empty life you inherited from your ancestors. And the ransom he paid was not mere gold or silver. It was the precious blood of Christ, the sinless, spotless Lamb of God. God chose him as your ransom long before the world began, but he has now revealed him to you in these last days. (1 Peter 1:18-20, NLT)
Great answers already, here's another take. Since you are looking for what knowledge God might have had before Jesus came to Earth1, let's look at words that were written before then, by the prophet Isaiah (53:4-9):
Surely he took up our pain and bore our suffering, yet we considered him punished by God, stricken by him, and afflicted.
But he was pierced for our transgressions, he was crushed for our iniquities; the punishment that brought us peace was on him, and by his wounds we are healed.
We all, like sheep, have gone astray, each of us has turned to our own way; and the Lord has laid on him the iniquity of us all.
He was oppressed and afflicted, yet he did not open his mouth; he was led like a lamb to the slaughter, and as a sheep before its shearers is silent, so he did not open his mouth.
By oppression and judgment he was taken away. Yet who of his generation protested?
For he was cut off from the land of the living; for the transgression of my people he was punished.
He was assigned a grave with the wicked, and with the rich in his death, though he had done no violence, nor was any deceit in his mouth.
The bold parts speak either directly or indirectly of His death.
So clearly the answer to your question is, "Yes, according the Bible God knew Jesus would die before He came to Earth." However, you specifically ask about crucifixion - the manner of death is not specified in this passage (nor anywhere else in the Old Testament).
Reference: the full text on Jesus' death from Isaiah: Isaiah 52:13-53:12.
1 Many, probably most, Christians believe that God knows everything all the time, so it is not possible for Him to learn something new. If this is true, He would know everything about Jesus death (time, manner, etc) before even the creation of the world (reference God's knowledge of Jeremiah).