Imho:
- He's got CoA down. We had 3 levels already, being basic hardening, the shockwave one is the next stage, and internal destuction (Luffy's Roc Moves). Id actually say AdCoC is technically stage 4 year and not a level of CoC by itself.
- CoO, he's barely mastered the 2nd stage, FS imo. FS mastery is what he needs to learn here with Kizaru i think. Finally whatever 3rd stage is probably (?) Shanks' FS killer thing. To go beyond and essentially trick the person into seeing the wrong future? Not sure.....
- CoC has the basic one we know, then i would "assume" stage 2 is the thing Shanks pulled on Ryokugyuu. Stage 3 is not known yet?
All in all, highly subjective and confusing.
VoAT is a totally separate thing imo. Probably an adjunct to CoO, but its not a "power" with combat ability.
AdCoC is just an application to Hardening. Its not necessarily a "stage" in Conquerors imo, but thats just me.