Question and answers
Will grating Divine Protection to a squire reveal the squire to the guardian?
Yes, even though it is not -regular- protection such as Bodyguard, it still triggers the Squire ability.
What happens if a Mirror Beast mimics the ability of a Squire? Will it turn into a town defender?
The Mirror Beast can never become anything but a wolf role. But if a Squire is lynched, and the Mirror Beast is protected, the Squire ability would trigger and unfortunately reveal the Mirror Beast to the protector.