Can we add CD singles sent by record companies (usually Warner, Polygram, etc.) to radio stations with the mention "for promotional use only - not for sale" ? These have usually 1 song only, sometimes in "edit" version. They have a nice professional cover. I have a few of those at home.

Sorry, couldn't find this info anywhere. I saw "do not add samplers", but those singles are actual versions meant to be played on the radio, not "samples". If they are edits, they are done in a way that the song has a beginning and an end. It may be that the guitar solo is shorter.

No, a release must have been publicly available at some point.