Hey happy to help, for rules for any category there is a button next to submit run that will outline the specific rule differences for said category. To answer your question a level 6 run requires you to equip the cursed ring and keep it equipped for the full duration of the run, this prevents you from leveling Zack and his materia(This is essentially your level 1 run for this game, you just don't start at level 1 like most other games).