Limits of Divine Magic

This lore was among the conjurer's tools found in the cave beneath Dooptopia, where Magusar was first encountered..

Rigorous testing has proven that the overwhelming majority of magic spells granted by gods will only function within three hundred miles of a temple or shrine to the spells parent-god.

Other than their spells, there is no way of knowing for sure if a god can hear or is acting on our prayers. Can we surmise from here that gods have no power at all in areas that are a great distance from any of their shrines?

If this is true, if one were to summon a god from a very remote and removed location, that gods manifestation would not have access to it's followers devotion and would be powered solely by the summoner. A single mortal provides a pitiful measure of godly power, so the god that was summoned in this scenario would be extremely weak.

If all of the above proves correct, might it be possible for a simple mortal of no divine power to overpower a god, given the proper conditions?