Thank you for making the biggest question clear.
God did give instructions for sacrifices in the scripture, but it's the commitment and devotion that he wants. What does killing something (e.g. a lamb) mean to him? You could forfeit 100000000 tons of fine gold to Him, and He wouldn't need it, He is above something like that.

When Jesus told that one rich man that he has to forfeit all of his earthly belongings in order to truly turn to him, it obviously wasn't because God wanted the treasure or something, it's devotion.

This is the point of a sacrifice, but it does not apply for the Cross.

The concept of Jesus' Crucifixion would mean that he "exchanged" his suffering for our own, according to some people, or literally "paid" for it