OK, so you have:
Board: 3⋄ 9♠ A♠ 4♠ 8♠
Player 1: Q♠ 9⋄
Player 2: K♠ J⋄
Player 3: Q♣ 5♠
Well, combining the 5 best cards, each player will have:
Player 1: A flush: A♠ Q♠ 9♠ 8♠ 4♠
Player 2: A flush: A♠ K♠ 9♠ 8♠ 4&...
The point of hold-em is that your hand is the best possible five-card combination from all seven cards. So, in this case, yes, it is a split pot. All players (as you describe them) have a 6-high straight. That's the best possible hand, so that's their hand.
There are a ton of questions here.
Was it a good move to open against a loose-agressive BB cheapleader with a K J off suit holding?
The problem with opening this weak against LAGs is precisely the problem you described. You simply have no idea where you are. There you were, in position, against the blinds, and you had no idea where you were in ...
Not every hand has to have both blinds. In some games, when the BB from the previous hand leaves the table, the SB becomes dealer and there is no SB for the next hand. I think that's what you're seeing here.
So although the game is normally 5/10, for this hand there's only a single 10 ante by player 1.
Looking at the game preceding this one in the ...
I would say it's player dependent. I sometimes min-raise the river as a bluff against a good player, because most thinking players interpret the play as me having a strong hand. But don't do it very often. If it is some old guy at the card room that's min-raising you, he almost always has a good hand. If you know you're beat, just fold. Curiosity can cost ...
Assuming you are playing Texas Hold'em. Its the best 5 card hand using ANY combination of your hole cards (Cards in your hand) and the community cards (cards on the table).
You won the hand with a pair of Aces. Pair of Aces > Pair of Queens.