In the FR universe, before Mystra's ban, spells up to 12th level could be cast relatively easily by mortals. It’s safe to assume the gods could do the same.
Were the gods affected by the ban on spells higher than 9th level? Could a god theoretically slice off a mountain and flip it, or seal off a crystal sphere? They were innocent in this matter, and surely if anyone could be trusted with this responsibility, it would be the gods.
Is there any reference to Mystra's ban that mentions whether such limitations were imposed on deities?