AKo vs cold 4bet shove preflop

A not fullstack player is not always a fish, he could even be just a bad regular.
I would just fold here, and continue with KK+, maybe QQ because of his stack size. You need BB to push many Ax combos here to be ahead, and since you haven't invested much in this spot, calling his AI would come along with a lot of variance.

vs fish -> call, vs reg -> fold.
if you always fold it's alright, remember you only invested 2.5

That's what I figured, I'm not losing/gaining much equity in the long run there I think?

well EV of folding = 0

so what about calling?
since you're calling such a massively huge "overbet", you need to be close to ahead of BB's range (you cannot call against AK,QQ+ range as you have only ~39%)
and SB is still uncapped and might be ahead of you as well. i think it's a relatively not difficult fold

Snapcall when he is fish. get sucked out by A3o.

It’s a huge cold 4-bet here. I think most people don’t push AI like that. It’s probably AA or KK, and then we’re almost dead. Having invested just the original raise, I’d be happy to fold this without reads that he likes to bluff 4-bet a lot or overplays weaker hands that way.

Viliain looks like fish, but sample is too small, and we don't know how he play. Nobody write about SB squeese, he also can have big hand, fold is best imo.

I think folding is a good option here. We have invested so little and we need so much equity to break even here.

Yes, as pretty much everybody said you could just fold here, and wait for another spot.

And what about the fact that there are players yet to act and that can join the pot? Is this good for a call or is it not?

Then you need off course less equity if 1 of the players behind will call, but then you are most likely even in worse shape if that will happen. Especially the SB will only call with premiums if we would stack off.

Cheers,
SDK1987