Ответ:
1. I used to live in a flat when I was a child. (+)
Did I use to live in a flat when I was a child? (?)
I didn't use to live in a flat when I was a child. (×)
2. We used to go to the beach every summer. (+)
Did we use to go to the beach every summer? (?)
We didn't use to go to the beach every summer. (×)
3. She used to love eating chocolate, but now she hates it. (+)
Did she use to love eating chocolate? (?)
She didn't use to eating chocolate. (×)
4. He used to smoke. (+)
Did he use to smoke? (?)
He didn't use to smoke. (×)
5. I used to play tennis when I was at school. (+)
Did I use to play tennis when I was at school? (?)
I didn't use to play tennis when I was at school. (×)
7. He used to play golf every weekend. (+)
Did he use to play golf every weekend? (?)
He didn't use to play golf every weekend. (×)