In UK/ England, the same rule works with the verb ‘have’ also. So when we say
I have a dream.
-Have I a dream? (Question)
Or, Do I have a dream? (Question)
-I have not a dream/ I haven’t a dream/ I don’t have a dream. (Negative)
So there are only two exceptions to the ‘do-insertion’ in question and in a negative sentence. These are with the verb ‘be’ and the verb ‘have’.
To put emphasis in imperative sentence
We also use the do-insertion with an imperative sentence when we want to put the emphasis.
Example:
Instead of saying to a kid,
“Behave!”
We can say, “Do behave!”
It means to put emphasis on ‘behave’ which is like giving an order.