To trigger the Werewolf's back face's transform ability, a single player must have cast two or more spells during the previous turn. If multiple players each cast just one spell during the previous turn, the ability won't trigger.

The abilities that transform a Werewolf back and forth look at the entire previous turn, even if the Werewolf with that ability wasn't on the battlefield for some or all of that turn.

If you control three Vildin-Pack Alphas and a Werewolf enters the battlefield under your control, you may transform it, transform it again, and transform it a third time.

If a creature with haste transforms and no longer has haste on the same turn that it comes under your control, such as if you cast a Geier Reach Bandit when you already control a Vildin-Pack Alpha and choose to transform it, it won’t be able to attack that turn.