Hey, what an interesting topic here. Let me contribute with some facts.
1) The following singles are metal ones. All of them are highly recommended to metal fans.
3 Kern (shame, each of their singles contains a ballad)
All the other singles are just for completists. They are not bad, but not metal, not even hard rock.
2) Yes, I have them all, at least I think so.
3) Some of them exist with different covers. No one of them is prior or posterior, as far as I know. All the old Czech metal singles have just universal factory covers. Only few bands had own 7inch picture cover (Citron, Kern). There is no difference if something comes in Galaxie cover or some other ones, like Poslouchate Vetrnik or some other no-name edition. But those are not real series like Rockmapa. Those are just universal cover for rock and alternative music. It does not automatically mean, that all of them are interesting. Far from it!!! Only some of them are metal, moreover some of the metal ones are titles from Rockmapa serie.
4) Background info? What exactly? There is a book, there was a serie of TV documents back those days... The responsible person was Petr Janda (gt and voc of Olympic, Czech rock band strongly influenced by metal in the late 80s, two of their albums can be labelled as metal ones)
5) Number 22 Vitacit: I have to say, wowgh! Anyone has it in collection? Or anyone have seen it in someone else´s collection? According to my informations, this does not exsit and number 22 is different, non-metal title (Odyssea).
1) You are right, LP Rockmapa vol.1 (except one song, it is pure metal compilation) and vol.2 (only one half is metal) exist only as LP. Vol.3 seems not to exist. Vol. 4 CD+MC (mostly metal).
2) Retez only released this singl and the same song on LP Rockmapa vol.2. Officially it is their complete discography, aside from this they only have some demo and studio recordings on tapes.