Q: If you were to use Gravity only for Pulverizer's ability, do you still need to have five Gravity cards?
A: As long as you don't use gravity cards, you don't have to use 5 of them. The rule is updated to reflect this.
Q: Lastly, any reason on the "no more than 3 Titans" rule?
A: Yes, a possible deck that would become too strong otherwise. I am not gonna explain this before the tournament is over.
Q: Are there going to be any stipulations on Discord? The card, not the player.
A: No, enjoy a tournament where Discord is neither banned nor restricted.