Hopefully it will help if you know it's an anagram of "e" (finally once) "or" twice and "page" and you are right about the opera bit. Who would be a fan of Cosi Fan Tutti?
1ac is a classic example of a Paul clue - guess the answer, then try to explain it. I don't think many wold be able to work "forwards" through it, though it does in fact make sense.