Adam and Eve were immortal as long as they had access to the tree of life... the bible never says they were made immortal. this the story makes clear in several ways, even in the book of revelations showing that the tree of life is brought back to human reach.
the seperant said they would not die [from eating of the tree of knowledge] which turned out to be true. God said they would [which turned out to be incomplete].
the story reads like- ok if you eat this you will die... you eat it and say, hey, I am still alive and then I shoot you in the head.
see I told you, you would die.
the meaning of the tree of knowledge of good and evil is not as clear...
first you have to think, how do you know what is good vs evil?
its not immediately apparent.. but it is always in reference to an ideal.
most of us have an ideal buried within us and we feel things are good or evil without anyone telling us... it is THIS ideal that the tree of knowledge was meant to block... God was in essance telling them, I am the ONLY one to tell you where to draw the line between good and evil not what you FEEL.
if you reject my line and draw your own you will be seperated [killed metaphorically] from me. [which in this case is likely not the real god, but the authors of the story who wanted power to reside in their government not in the hands of the mob.]