Man Had The Knowledge Of Good & Evil Before Eating The Apple In Eden (See Biblical proof)

Well I don't believe that the original sin has anything to do with eating of an apple but rather it is sexually related to me

, that is topic for another day,  this smart guy is saying something here, read and comment.

ACCORDING TO HIM,
In the book of Genesis 2:17 God told man

"but you must not eat from the tree of the knowledge of good and evil, for when you eat from it you will certainly die." 

And man understood what God meant.

This technically means that man already understood the concept of good and evil (Life and death) even when he had not tasted of the fruit of the tree.

So what was the essence of the punishment meted on Adam and Eve? 

What was the essence of the tree in there? Was it to test their inconsistency when it's obvious they were going to fail?