Hello,
The photo with the two seperate projectiles shows fakes that are meant to "impersonate" German WW2 2cm AP-HC-T projectiles, but not doing so very well.
Same for the photo showing the two rounds.
The other rounds:
#3 3cm Mk 212, experimental round, probably loaded with a "Minen" (HE) projectile. The shell cannot be considered safe unless it was de-milled by EOD. Allthough chances are that it is a "Minen-üb" (HE practice projectile).
#4 2cm Mk 213, an experimental round as well, loaded with an AP projectile. Same as with the 3cm Mk 212, projectile cannot be considered safe unless de-milled by EOD. Projectile could be AP-HE, AP-I or AP-practice (and may have tracer).
#5 and 6 20x119 Madsen, again as above, projectiles cannot be considered safe unless..
The left of the pair being an HE, HEI, or HE practice, with a high probability of a tracer being present.
The one on the right is an AP-HE-T-Sd (selfdestructing armourpiercing High Explosive).
The Madsen auto-cannon / ammo originate from Denmark, but was captured/copied by the Germans during WW2.
As for # 1 and 2 ... no clue, probably modern.
Edits: corrections to spelling/lay-out