Negations or questions with must vs (don't) have to
Question:
Auxiliary? Put the auxiliary 'must' at the beginning:
We must(n't) leave early. > Must(n't) we leave early?
No auxiliary? Use of do / does / did (+not) and infinitive:
He has to work hard.> Does he have to work hard?
(has to/had to are no auxiliaries)
He had to work hard. > Did he have to work hard?
Negation: We must leave early. > We musn't leave early. (auxiliary must)
He has to work hard. > He doesn't have to work hard.
He had to work hard.> He didn't have to work hard.