If you ask such a question, you must be a beginner learner so I will explain it without using many grammar terms:
In all your examples only one sentence is correct every time. "Is" is a main verb there. That means we translate it and it is the only verb in the sentence. For example:
What is it?
There is no other verb besides is, and this sentence is correct.
"Do" is not a main verb, it is used to make negatives and questions. There is always another verb in the sentence, which we translate. All the other sentences are examples of that; the verbs are: practice (first example), come (third example), matter (fourth example), care (fifth example), realize (sixth example).