Rengoku 2: The Stairway To H.E.A.V.E.N. Codes -

H.E.A.V.E.N.-A, -B and -C:
Defeat Gryphus in level 8. Then, re-enter Primordium (level 0) after the intermission sequence and enter the door behind you.

Highest H.E.A.V.E.N. floor:
Successfully complete all 99 H.E.A.V.E.N. levels.