Must be before End Date
Must be after Start Date
I recommend joining the official Halo discord to see there's anyone who's interested. I'm not that fantastic at the game either, but I'm more than willing to help anyone with challenges or achievements if they need it. :)
The scarab skull doesn't void beating Halo 2 on legendary. Similarly, the bandana skull (infinite ammo) doesn't void beating Halo: CE on legendary.