***** NOT A TEACHER *****
I am not answering your question. I will leave that to more qualified members.
I just wanted to tell you how I would handle those conversations. (I cannot speak for anyone else.)
(Mona and I are looking at an album)
Mona: Is this a photo of Igor?
James: No, it isn't. It's me. ["Book English": It's I. But 99% (?) of native speakers ignore the rule.]
(I knock on Mona's door. She was EXPECTING Raul.)
Mona: Raul? / Is that you, Raul?
James: No, it isn't. It's me.
Mona: Who is it? / Who is "me"? [the second question is humorous and perhaps a bit sarcastic]
James: Don't you recognize my voice?
Mona: Oh, is that you, Jimmy?
James: Of course.