Villain is active 3bettor over small sample.

PokerStars Zoom, Hold'em No Limit - $0.02/$0.05 - 6 players
Hand delivered by Upswing Poker

UTG: $3.45 (69 bb)
MP: $5.00 (100 bb)
CO (Hero): $6.18 (124 bb)
BU: $5.00 (100 bb)
SB: $4.02 (80 bb)
BB: $8.49 (170 bb)

Pre-Flop: ($0.07) Hero is CO with 9♥ 9♠
UTG calls $0.05, 1 fold, Hero raises to $0.25, BTN 3-bets to $0.75, 3 players fold, Hero calls $0.50

Flop: ($1.62) 7♥ J♥ T♣ (2 players)
Hero checks, BTN bets $0.47, Hero calls $0.47

Turn: ($2.56) 5♦ (2 players)
Hero checks, BTN bets $1.30, CO (Hero) ??

I think the early limp makes it more likely btn is 3betting light. So maybe I can 4b/gii pre.

As played does anyone like a turn shove? He can barrel basically any two broadways.

I play same limit and would fold the turn here against an unknown. Basically, he's committing you to this pot after showing strength on every street. Most opponents won't play AK or AQ, even hh, (or 88>) this way, they'll typically show you AJ or a set of 10s or some such.

The problem with small samples is that maybe the villain is an active 3-bettor, or maybe they happen to have been catching cards.

I think the opposite is true: the early limp increases the likelihood that the villain's three-bet will be called by somebody, and so (if they know what they are doing) they will be three-betting a linear range, not a polarized one.

The bet we are facing is just big enough that we are barely getting the right implied-odds price to set-mine, without taking into consideration that we are out of position and it will therefore be difficult for us to stack the villain.

I do not like flat-calling three-bets out of position. I do not think 99 is a good candidate for a four-bet, as it blocks none of the villain's strongest hands the way A5s or KTs do.

It may sound nitty, but I think there is an argument for folding when the action comes back to us preflop.

As played preflop, I think the villain's c-bet prices us in to draw to our gutshot and backdoor hearts. I see no good in raising, as that would make the villain fold their air but call with all the hands that beat us.

Turn is a clear fold. Villain is in the happy position of being able to take free cards when they need them and bet when they have a value hand. Maybe, as you say, they are barreling with two broadway cards. Are you willing to bet your entire stack that they are?

Our best defense against a villain who may be three-betting widely is to tighten our opening and isolating ranges (to fact those three-bets with a stronger range), to size down our opens slightly (to reduce the cost of getting three-bet), and to bring a robust four-betting strategy to bear. If we have a well-thought-out strategy, we know what to do with each part of our range.

5x is a little excessive after the 1 limper imo, 4x would be fine. being oop really sucks but i think flatting the 3b is still correct, trying to gii with 99 seems excessive unless you've established an aggressive dynamic with the guy. not saying i'd 4b entirely polarized but at least polarized enough that 99 is a flat most of the time

I might consider x raising the flop if villains cbet is high. Denies equity to villains equity bluffs. AP fold turn don't shove here.

Probably fold pre, when he 3bets you after you've 5x raised an UTG limp he's gonna have a pretty strong hand and you're OOP. Anything other than a 9 on the flop and you're gonna be facing a difficult decision, even if the flop is all low cards he can put you in a tricky spot with all of the overpairs in his range.

You only really ahead of AK & QK on the turn, the latter of which still has a lot of equity and maybe a couple of complete bluffs - but he should usually give these up on the turn. Even if you call the turn and spike a 9 on the river you're losing to a lot of his range.

AP calling flop is fine, but I think folding turn is correct.