Asking questions isn't very useful unless you can propose a way of looking for answers. Humans can hypothesize gods and look for them. Gods could look for "supergods". What would a supreme being look for?
I disagree, anybody can ask questions but they may not be qualified to propose a suitable test for the answer.
Then they need to ask somebody who is qualified. Of course, somebody who is more qualified than the "supreme being" doesn't exist, so it would be useless for him to ask himself such questions.