So... my TAG got possessed under a self-owned assault hacker. When my enemy activates it, can I try to possess it back?
The problem is that "being possessed back" (or something similar) is no cancelation clause for the initial possession.
Wouldn't the second Possession override a number of effects from the initial possession? Essentially you would get your TAG back to use but using the Possessed Profile. Though it would count as a casualty and not generate an order etc?
Yes, that's the correct answer. Your re-possessed TAG will still have the possessed status and profile.
And considering Exorcism is an attack, you can't un-hack it with a (Defensive) Hacking Device if you possessed a possessed TAG