1) Villian unknown. No reads/stats. Do anything differently?

PokerStars No-Limit Hold'em, $4 BB (6 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

CO ($394)
Button ($241)
SB ($404)
BB ($402.60)
UTG ($318.35)
Hero ($406)

Preflop: Hero is MP with A, K.
1 fold, Hero raises to $16, CO raises to $44, 3 folds, Hero calls $28.

Flop: ($94) 6, A, A (2 players)
Hero checks, CO checks.

Turn: ($94) 4 (2 players)
Hero bets $60, CO calls $60.

River: ($214) 9 (2 players)
Hero bets $124, CO raises to $248, Hero calls $124.

Final Pot: $710

2) Villian is a very solid Tag regular. He is very very aggressive, and definitely capable of pushing this flop as a bluff, semi-bluff, or with the goods.

PokerStars No-Limit Hold'em, $4 BB (5 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

SB ($397.50)
BB ($621.80)
UTG ($541.40)
MP ($396)
Hero ($813.80)

Preflop: Hero is Button with K, J.
1 fold, MP raises to $16, Hero raises to $52, 2 folds, MP calls $36.

Flop: ($110) K, 4, 4 (2 players)
MP checks, Hero bets $72, MP raises to $344, Hero ? (it's $272 more to call)

3) Same villian as in hand 2. Normally I raise this flop or even reraise preflop, but against these super aggro players, I sometimes find it better to take a more passive line, in hopes that I make a hand and let them bluff at it. Play it any differently?

PokerStars No-Limit Hold'em, $4 BB (4 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

UTG ($538.30)
Button ($350.60)
SB ($432.90)
Hero ($1370.60)

Preflop: Hero is BB with A, T.
2 folds, SB raises to $16, Hero calls $12.

Flop: ($32) 7, 9, 7 (2 players)
SB bets $28, Hero calls $28.

Turn: ($88) T (2 players)
SB bets $80, Hero calls $80.

River: ($248) 9 (2 players)
SB checks, Hero checks.

Final Pot: $248