The rules for Nuzlocke are for the most part not set in stone, you can adjust them to fit almost level of difficulty you wish.

Not directly stated, but if you save and a Pokemon faints you may not reset to before the event.
Extra restrictions include:
- Level restrictions (staggered by gym) to prevent serious overlevelling
- Forcing teams to be evenly levelled (e.g. your highest level Pokemon must not be more than 5 levels higher than your 4th highest level Pokemon, other than at the very start before you have time to level up your 4th Pokemon.)
- Pokecenters may only be used to heal PP not health or status
- No recovery moves.