You are correct that Scripture doesn't specifically say for Adam to tell Eve (or anybody else). But Scripture does record for us that Eve had it 2/3 correct which implies there was some amount of communication that happened b/t Adam & Eve.
She got correct that God didn't say she couldn't eat of ANY tree (refuting what Satan asked her). She also got correct that she was not to eat of the fruit of the tree of knowledge of good and evil. However, the kicker was she added to that and said she was not to touch it either. One of the take-aways for me is also repeated in Revelation - DO NOT ADD TO WHAT GOD SAYS.
For your other question The question is, when did Satan sin and why didn't his sin bring in death? Ultimately Satan's rebellion DOES usher in death - he convinces mankind that what God says is irrelevant and we can be our own God. Exactly what he was cast out of heaven for. I don't know of the scripture that records the "when" of that happening. Please educate me.
I don't know either, but we are not completly in the dark. If Satan was created, it would be between Genesis 1:1 and the meeting with Eve in the garden. Of course there were other things that would have had to happen in this time frame. Do we need a gap or gaps and if so where would they be?
Revelation 12 says "his tail drew the third part of the stars of heaven." The stars were made on the fourth day so if the stars are the fallen angels, that might suggest they were made on the fourth day.
Perhaps you already see a problem here. Genesis 2:3 seems to distinguish between "created" and "made" and nothing was created on day four.
The details in scripture give us much more than we recieve. Look closely at the details.
I'm headed out right now we can discuss more later if you like.
Seven