1. Venus is jealous of Psyche because men began to worship Psyche for her beauty, even though she is only a human and would not live forever like a god or goddess. It ultimately doesn't make much sense for the goddess of love and beauty to be jealous because the idea of jealousy can't be described as something beautiful as it mostly a destructive thing.
4. I think that it is fair for Cupid to expect Psyche not to be curious about his appearance and that it is wrong for Psyche to have taken a peek because I don't think Cupid could be faulted for believing that if Psyche really loves him then it shouldn't matter what he looks like.