When we form a Past tense question or negative sentence, we use the 'helping' verb 'did'. 'Did' is already in the Past tense, and there is no need to use the Past tense for the main verb too. I asked him.

Did you ask or have you asked?

However, if (for example) you were talking about something that happened last year, "Did you ask her?" would ask whether, at that time, you asked her the question; "Have you asked her?" would ask whether you asked her at any time between then and now.

Did not ask or did not asked?

"I didn't ask" is correct. "I didn't asked" is wrong.