Temporary servants are regular servants unless you haven't achieved the unlock by the event end date. If you do something, it doesn't disappear when unlocked. The materials are wasted if you don't unlock them in time though.

So, if I ascend Iyo to her max and add 1 np copy to her, and then unlock her permanately, she will still have those things?

Yes. Exactly as you said.

Oh okay. I just didn't had a temporary servant for a while, so I forgot how they work bc I don't want to accidentally use them and then after getting perm one I can't ascend her up due to lack of the crystals that should be use for it

Of course, they will perish if you didn't meet the specific requirements. Welfare servants always go in "Temporary" state, it indicates that you need to finish the main quest of an event so they can stay in your roster permanently. Don't worry for that, because the event is just starting right now.

I know but you know, glitch may happen or smth else and I kinda need her with Oda to help her defeat Demeter, at which Im stuck on because she is too strong

IMO, Demeter is not that hard as long as you have low-star riders like Ushiwakamaru, and Mandricardo.

Demeter is not hard if you know her skill pattern:

Turn 1 : Defense up + Damage Cut

Turn 2 : 3 NP charge + Attack up (1 hit)

Turn 3 : Remove debuff + heals + debuff immune

Those skills always repeated Every 3 Turn or whenever you break her HP bar.