Can we call this 4bet given the small size? Havent got much stats or info on vilian

Calling that bet oop to fold the flop is burning money imo. As played... That's not a bad flop actually. If he has exactly King King you're getting about 35% on a pile so this might not be a bad spot to donk pile if we aren't shoving pre.

Didn't consider donkshoving, but that seems very reasonable thank you!
Can we really fold if we need just 26% equity?

no its not.

You're overfolding if you fold this hand pre, but it's a spot you could potentially get away with an explo. I'm very skeptical whenever a player at these stakes commits themselves without shoving.

You should certainly have stop-n-go in your playbook when you're flatting 4!s OOP, and this is a great board to rep a lot without over-compromising your checking range. The problem is that AK has so much equity here that you have to be careful about how you construct your range. You have to ship TT, QQ, and JTs and only ship the AQo combos with the A of diamonds in order to make AK indifferent to a call.

EDIT: PIO doesn't have an open-shipping range here and goes with a very straightforward strategy of checking and folding 55% to a shove. The bottom of its calling range is AK with a diamond.