About the usage of did.

Usually ‘did’ is not used with the question word ‘who’. Could u please help me in this regard.

Hi. “Did” can be used with “who” where it is an interrogative pronoun.

Who did it?
Who does it?

Hello and welcome to the forums.
Where did you learn that?

Who did this work?
Who did you ask?

I think you might mean 'did ’ is not used with ‘who + a different verb’:

Who worked on that?
Who asked for your advice? (

Often ‘did’ can still be used, and this adds greater emphasis:
Who did ask for your advice?