Will state what I feel like I did incorrectly after a few comments. No peeking precomment
Just sat down this was my second hand at the table - never played with villain MP3 before so assume he's the standard 5c 10c fish.

Ultimate Bet No-Limit Hold'em, $.10 BB (10 handed) FTR converter on zerodivide.cx

Button ($4.60)
Hero ($9.90)
BB ($10.45)
UTG ($4.55)
UTG+1 ($18.15)
UTG+2 ($4.27)
MP1 ($6.35)
MP2 ($9.64)
MP3 ($12.17)
CO ($12.35)

Preflop: Hero is SB with J, J.
UTG+1 raises to $0.25, UTG+2 calls $0.25, 2 folds, MP3 calls $0.25, 2 folds, Hero calls $0.20, 1 fold.

Flop: ($1.10) 9, J, 4 (5 players)
Hero bets $0.8, UTG+1 folds, UTG+2 folds, MP3 calls $0.80.

Turn: ($2.70) Q (3 players)
Hero bets $1, MP3 calls $1.

River: ($4.70) 7 (3 players)

I was a little worried about the turn as it completed a straight, thus the non 2/3 pot bet there...and who calls a 2/3 pot bet on this flop besides trips, KJ/AJ/QJ/JT, 8T unless the player is just a complete fish?

3 questions - reraise with JJ in the SB here? Bet more on the flop with so many involved? And lastly - check behind on the river?

Results in white:

[Hero bets $1.25, MP3 raises to $2.5, Hero calls $1.25.
MP3 shows T of clubs 8 of clubs
MP3 wins
Final Pot: $9.70