not a teacher
QA) If a person introduces himself and you cannot hear him clearly, what is the proper way to ask again?
Pardon me, what is your name again?
I beg your pardon?
QB) If a person contacted you (email/talk to you in person), but you cannot remember him, what is the proper way to ask how does he know you(how he came to know you)?
Excuse me, I am trying to recall if we have spoken before/ you have emailed me before.
QC) When a person is exchanging contact with you, do you ask him how to spell it? Do you ask for first name? What is the proper way to ask it?
How do you spell your name please?
Student or Learner