in any question-answer confrontation, if the querent asks "why?" enough times, the respondent will eventually be reduced to saying "because!"
there may or may not be ultimate answers in this sidereal universe - but it is unlikely that the human mind could encompas them or express them.
Yes, but when you reach the stage of "because!" the answer is not really "because!"; the real answer is: "because no one has ever observed otherwise and no one can think of any plausible way that it could be otherwise!"
Not necessarily. GR evidently allows time-like loops. IIRC Goedel had a (admittedly unlikely) model in which a causal universe arises from space-time region filled with them. On such a loop the sequence of causes loop back on themselves.