Turn to Frog

Turn to Frog doesn’t counter abilities that have already triggered or been activated. In particular, there is no way to cast this spell to stop a creature’s ability that says “At the beginning of your upkeep,” “When this creature enters the battlefield,” or similar from triggering.

If one of the Theros block Gods is affected by Turn to Frog, it will be a legendary 1/1 blue Frog enchantment creature with no abilities. If it stops being a creature, perhaps because your devotion to its color(s) decreased, it will be a legendary blue enchantment with no abilities. The way continuous effects work, the God’s type-changing ability is applied before the effect that removes that ability is applied.

If the affected creature gains an ability after Turn to Frog resolves, it will keep that ability.