not really an answers, but "didn't you used to have dog?" sounds more natural Also some would say "Did you not have a dog?" I think this is a nice way of saying it, I think people from Northern Ireland and Scotland often speak this way, they have an elegant/dramatic way of saying it with the emphasis on 'not'. It sounds poetic I think. Helps to have a Scots or N Ireland accent though!!

Did you used to have a dog? is a question that can be asked on its own . Did you have a dog? is a question that needs some clarity. For example: Did you ever have a dog? Did you have a dog last year? Did you have a dog as a child?

Did you use to have a dog? (It means he or she used to have a dog in the past but now she or he does not have a dog anymore). Did you have a dog? (Maybe you have a dog or maybe not dependson the situation given)

used to = past tense of present simple present simple = habits you still have now used to = habits you had back then The past simple refers to time in the past, and implies a single action or state. In the case of verbs like "have" there can be very little difference between the two. But in the case of action verbs the difference is huge.

didn't / We / use to / a dog / have