True form Aiwass, True Form Coronzon, Full Power MGs, Zombie Layered MGs, Othinus and Alice aren't included in any of the 3, nor is Tsuchimikado or any other esper who knows magic.
Really small cameos/participations such as Ollerus in the end of OT and Anna at the end of NT won't have these characters included in these series.
Characters who got stronger versions of themselves in a series after their introduction won't have that form nor weaker ones in the 2nd/3rd series they appeared, for example, Aleister (base or otherwise) isn't included in NT and GT, Abyss Crosser Aleister isn't included in NT even tho it was introduced there (keep in mind this is for actually new forms/power ups/spells, specific cases such as Blood Sacrifice Aleister, which was introduced in NT but that he could use back in OT aren't included in this rule, if we can't be sure if a form/spell/whatever could be used they will be fully excluded as if they were new).
Characters who got weaker are included as their strongest versions.
Characters that were first introduced in the mangas/side stories before the main LNs will be included in the series they'd be a part of by in-verse chronology.
The 3 composites share the same goal of defeating each other and are not going to team up willingly.
The battle takes place in an indestructible planet Earth and starts inside of Academy City.
KO, Incap, BFR and Death are all valid incons.