Ответ:
1. I have to study French
.
2. 'Does Harry have to get up early?' 'No, he doesn't.' [Does + He, she, it + 
; базовая форма глагола без окончания!]
3. We have to get to school before 8.30 a.m.
[Не забываем ставить 'to']
4. Jason and Sarah have to wear a uniform. [Jason and Sarah - they (они)]
5. 'Do you have to stay at school for lunch?' 'Yes, I do' [В кратких ответах ставим вспомогательный глагол - здесь это do]
6. We don't have to do homework at the weekend. [I, you, we, they + don't + ]