No is its past tense, no = no. Note: do is the third form of do. The same: not done = not done, should not = should not = should not = will not.
Usage of do:
1 and do are used to form the interrogative or negative forms of simple present tense and simple past tense, followed by prototype verbs. In interrogative sentences, do is grammatically necessary, but it can be omitted customarily (sometimes with a subject), especially in spoken English.
2. When there are negative adverbs such as never, rarely, almost, almost, rarely, etc. In a sentence, these adverbs can be moved to the beginning of the sentence to emphasize the mood, and placed before do to emphasize the mood. At this point, they are one of the inverted structures.
3.do is used in imperative sentences to express an order, an invitation, a suggestion or an explanation.
4.do can also be used as a substitute verb to make the language concise. Do so is used to indicate actions that have been done or mentioned before by the same subject, and the objects and adverbials involved in verbs can also be replaced by do it or do that; Do that has a heavier tone than do it, and it is not stressed in the sentence, but that should be stressed; Do so is generally not used as a state verb to express psychological, emotional or unconscious behavior.