Question tags at the end of the sentences

I have 2 questions:

First, Which one is true between:

I'm not your friend, am I?

Or

I'm not your friend, are I?

I was confused since I knew we had to use aren't I instead of amn't I as question tags on positive sentences.

Secondly, and related to aren't I for positive senteces, generally people use ain't I. Is the term ain't I standard?

The question comes after the comma and it is Am I your friend?

Certainly Are I your friend? would clearly not be correct.

The contracted phrase question gets stuck to the statement to ask if it is indeed not the case.

Use of ain't can be left to those who are trying to emphasize their rural, supposedly less literate, background