All the NT post-dates the crucifixion. Though if you do take the suffering servant of Isaiah as being about Jesus then that predates it.
I’d say there is definitely a lot of post-Easter faith retrojected back onto the lips of Jesus in the NT. How to Navigate the Cross and all that scripture as Christians is an important matter to me. In Matthew Jesus says you have to take up your cross but I am not sure that is even reasonable before he was crucified.
I think Jesus figured out he was going to die shortly before it happened. He prayed and made His peace with God and understood it was his will to go along with it and allow it to happen. That death was turned into salvation for many.
You can certainly believe God gave us his Son in the sense that he allowed it. But any systematic theology text will at least lay out all the scripture supporting various models of atonement. Scripture describes the death of Jesus in numerous ways and most Christian’s and the New Testament itself believe the Cross was a pivotal event in human history that somehow changed the nature of things. It also seems to be described as a predestined event but I’m not a Calvinist so I have to ignore plenty of other predestination/election verses.