THe R stamp is for repairs and Alterations, defined in NBIC. However, requirements from ASME Section I or Section VIII as applicable will still be required, as defined in NBIC.
The A stamp can cover Section I and BEP, since BEP refers to Section I requirements anyway. The PP stamp can be used for BEP only. For myself, I have to say I don't really understand why BEP in 31.1 exists since its essentially Section I. Perhaps someone can explain this to me. I suspect the reason is lost in the history of the evolution of these codes. It certainly confuses me.
You can hold all of these stamps together or independently depending upon your scope of work.