This is not an AF specific forum, but most questions are about AF stuff.

I do not know the differences between USAF and USMC flight qualifications, selections, etc.

ROTC is a college program.  There are several commissioning programs for each service.  ROTC, the respective service academy (USAFA for AF, USNA for navy/marines), or OCS.  That will enable one to be commissioned as an officer.  To get a pilot slot is a further step beyond that.  (After this point, I don't know much about the USMC side of things).