"Standard" Definition/Terms @ 'PLR' & 'MRR'?

I am looking into obtaining articles with PLR &/or MRR.

I'm wondering if there is any standard definition for them, as to what terms & rights should go with the articles sold with them, which are accepted as common practice around the industry.

Specifically:

1) If/when I sell an article with PLR, can I do so in my name, as though it were my article, or do I need to leave the author's name & signature line in tact?

2) If/when I sell an article with MRR, does the person I sell the article to automatically have the right to resell it in his/her name with either PLR or MRR, or both .. or only if I grant them either or both?

3) Do I have to provide the buyer with the list of terms or rights that I commonly see with the few PLR articles I have bought in the past?

4) Am I under any obligation (legally &/or ethically) to disclose to the (prospective) buyer that these are PLR/MRR articles, or that I am not the original author?

5) For that matter, how do I know, or how can I find out, whether the person selling me these PLR/MRR articles - or at least the very first person to start selling them - had the (legal) right to sell them ... that they are not in violation of copyright law?

6) Is there some kind of 'authority' site I can check with, or is this something that just evolved as common practice, without any standard definitions or terms in place?

Thanks,
Richard