If you could find out the answer to one question about something objective about the universe that would make you happy, what would it be? (so no questions like "will I ever get married?" Will the Cubs win the world series in my lifetime?" etc. it's supposed to be something theoretically answerable now)
what would it be?
is there an afterlife?
is there a God?
is time travel possible?
is there intelligent life on other planets?
those are examples of what I mean
All of your examples are grammatically yes-no questions, while your description doesn't seem to mandate that. So, in the first place, I'm wondering whether I'd be restricted to asking a yes-no question.
Secondly, your parenthetical temporal restriction that the question
must be theoretically answerable
now is incompatible with at least one of your examples, namely number four, "is there intelligent life on other planets?", because in order for the question to be a valid one to ask under such a restriction, the asker must already be assured that there is enough
currently available evidence to decide it, which would all but eliminate the need to pose it to something like a magic oracle in the first place. The whole idea of a magic oracle is that it knows things that are generally out of the reach of mortals, including things that are impossible for them to verify,
at least at present, but which are nevertheless true. In addition, seeing to the far corners of the universe, that are beyond our ability to observe and that will remain so for the foreseeable future, if not indefinitely, is at least as magical as seeing into the future. That parenthetical temporal restriction doesn't seem thoroughly thought out.
Put concretely: what if the closest intelligent life exists a billion light years away? How are we going to verify that?
Thirdly, finding out the answer is supposed to make me happy? Again your examples seem relatively limited. The examples seem like they're taken from a greatest hits list of philosophical and scientific questions. Other sorts of purely personal questions, that fit the description of inquiring on something objective about the universe
implicitly, might make a person happier to know the answer to than any of those sorts of questions.
For example, assuming the question need not be yes-no, asking
How does any given person find a way of obtaining happiness?
might be worth considering. It's worth thinking about whether the objectivity is implicit in the question and whether the question is answerable, and/or whether the inability of some people to find happiness would be indicated in the answer, since getting a road map to happiness in return should go a really, really long way to providing a key to happiness.
However, assuming the question need not be yes-no, and that the intent is to stick close to the philosophical and scientific greatest hits, I'd actually consider asking
What is objective reality?
assuming, for one thing, that I'd have convinced myself, or the oracle would agree, that if objective reality doesn't really exist then that should be clear from the answer.