unless your point is it should already have fire immunity then idk who made them to tell you if they do or not, either way if it has the spell it will probably cast it since the AI cheats
yea the AI knows how to counter spell, but they have to have the spell for it
if you go invis in front of mobs that have blind sight or see invis they will cast it, they know the strength of dispel and if you are low enough CL where it will take buffs they will use it and if you are high enough CL where it wont do anything they dont bother
thing is their spell lists are not that great so even tho they can they are limited