I assume this is standard, yes yes?

Party Poker
No Limit Holdem Ring game
Blinds: $0.50/$1
6 players


Stack sizes:
UTG: $198.40
UTG+1: $103.37
CO: $86.16
Button: $23.49
Hero: $99.00
BB: $94.52

Pre-flop: (6 players) Hero is SB with
UTG calls, UTG+1 folds, CO calls, Button folds, Hero calls, BB raises to $2, UTG calls, CO calls, Hero calls.

Flop: ($8, 4 players)
Hero checks, BB bets $3, 2 folds, Hero calls.

Turn: ($14, 2 players)
Hero bets $12, BB calls.

River: ($38, 2 players)
Hero bets $28, BB raises all-in $77.52, Hero folds.
Uncalled bets: $49.52 returned to BB.

Results:
Final pot: $94

Against an unknown player, how high does my flush need to be before I can call this or do I always need a full?

Looks a lot like a boat to me. That weak flop bet after the minraise on the flop = very setty, combined with the river raise = you're beaten. Nicely played all the way through IMO.