At the time, the Fellowship was studying Genesis, so all of their questions pertain to events in the Garden of Eden. These are legitimate questions, even though the Bible simply does NOT answer them. Maybe he thought death was not horrible and therefore he ate the fruit to see what would happen. God first spoke to Adam in Genesis 1.28.
People normally learn language during their childhood.
Perhaps Adam thought God was lying when God said that eating the fruit would cause death. Moreover, Adam may have decided he did not want to obey and serve God, but instead wanted to be independent of God. In Genesis 3.22, it is made clear that Adam was correct - he did come to understand good and evil. Accordingly, it was Adam's responsibility to both warn and defend his wife from eating of the forbidden fruit. He may have done the former, but he very definitely did not do the latter.