So? The ability to understand the words, and the meaning of the words, is different than understanding the moral implications of the command. Without the knowledge of "good" and "evil", there is NO concept of "should" and "should not".
Which is precisely why the mechanism was trust.
The existence of other trees in the garden matters because it simplified the command even more.
You might counter that they shouldn't have believed or trusted anything anyone else said. But upon what basis do they have the ability to make that judgement? The idea that they are being deceived is derived from the knowledge of good and evil. If they are to "trust" God, then they would "distrust" others. What reason would they have to "distrust" others, except for the possibility they may be deceived, and that's beyond their ability to discern of even "know" at that moment.
Again, the command was extraordinarily simple. You make a good point that they didn't yet know good from evil at this juncture. But this just emphasized the importance of trust. For Adam to do exactly what you stated above, to understand the words and do accordingly with the words for no other reason than because his Creator told him to....versus doing according to the words of the snake, if for no other reason than because they were not like the words of God.
Ok. What do you mean by "better"?
Adam understood that he was not God. He understood that he didn't know how to create things, like God created the garden and his wife Eve. He understood that God knew how to manipulate energy better to accomplish creation. Because God knew these things better, God was superior. So he understood that God gave him instructions, and he followed them. He knew God was in charge. Adam understood he was subservient to God.
If a mentally retarded child takes a candy bar from a store, do we dole out the death penalty?
Adam was mentally capable enough to grasp he wasn't God and subsequently be subservient to him.Therefore, the command of staying away from that tree was further simplified by the fact that it would be just another manifestation of an existing and established pattern of obedience.