The tree of the knowledge of good and evil is also called the tree of the knowledge of blessing and calamity. All this anger about not being healed has to do with thinking God isn't blessing me. It's an effect of that knowledge with which I was born because of the original sin.
As soon as they had eaten and gained knowledge of their condition, which they perceived to be imperfect and shameful,they tried to hide from God. What am I trying to hide from God?
Cherubim are ministering spirits manifesting God's invisible presence (p. 27).
Why was Cain's offering unacceptable? Cain denied that he was a sinful creature under the sentence of Divine condemnation. He insisted on approaching God on the ground of personal worthiness. Instead of accepting God's way he offered to God the fruits of the ground which God had cursed. He presented the product of his own toil, the work of his own hands, and God refused to receive it (Arthur W. Pink in Gleanings in Genesis, condensed).
The Hebrew omits this clause, but various other tests show that it was originally included.
What God wants as a sacrifice is not the product of our own work. It is what He has given to us that we are to offer back to Him. It isn't a sacrifice to give what I can create on my own. I could just create more. To give what has been provided by God means that I trust Him to provide it again. To give God my vision, to allow Him to control what happens, to keep fromquestioning what He is doing, is my sacrifice. To offer up that kind of sacrifice is pure faith. What was wrong with Cain's sacrifice was the fact that He was refusing to trust God, believing that he had to please God instead of that God would accept him as he was.