Rebuy period spot with JJ

Are jacks trash here?

Not sure if this is 9max utg or 8max utg and what you mean by MP, whether HJ or LJ, but its gonna be a pretty close spot, where folding, cold4bet and probably even calling are gonna be pretty close. If its lower stakes tournament then good argument to just fold, because the 3better is probably tighter than supposed to be. Whatever you did, its not really an important spot to stress about, just another annoying close preflop spot with nice hand and ugly action.

It was an 8max, he was LJ, I shoved and he ofc had aces. It was a rebuy period so I justified it like that but I kinda knew I was an underdog but I jammed anyway. It was hard to rebuild my stack later tho

But ok let’s say I call him. Flop while showdown came 722. Can we get away here?

If you are going to 4 bet here you might choose 15 bb's (2.5x) rather than jamming. The 3-bettor isn't ever going to fold QQ+ to a jam. Then if Villain 5-bet jams you can fold.

Personally I typically call with JJ OTB here. Yes it looks like 99-JJ a lot but I'd rather go set mining than get it all in where I am only going to get called by QQ+/AK and some AQ which will be at best a flip. Also we get to play this in position.

The other thing to consider here is that UTG opened and Villain 3-bet. UTG will generally open tight and Villain should know this. So a 3-bet is likely to be strong. I doubt 88-TT would 3-bet here or at least rarely and a lot less than QQ+. Now because UTG has only 20 bb's Villain might care less about the range and want to isolate with a hand like AQ or TT. But it is close to 30% of Villain's stack so I would lean towards Villain has a big hand.

If you had called the 3-bet with JJ and flop is 722 you are going to have to call the cbet. Which might be like 4 bb's - 6 bb's. The turn will be toughest unless it is a A/K/Q/J... Villain will probably bet like 12 bb's which won't pot commit you. Sometimes Villain will check the turn which would make the river a tough spot not to call a 15+ bb bet. Here it will depend somewhat on your reads and how Villain has played up til now. Does Villain bluff much?