The Chess Set Up B6 System can be played against all moves that White can throw at you. To play the b6-system successfully you have to get familiar with the most popular setups and understand their strategic ideas.
This opening is fairly uncommon and seldom played and if you know it well you will most likely get an advantage over your opponent in a game as it is highly probable that you will know it better than he does.
However, let's get on with it. We are dealing with the three pawn setup here. There are two three-pawn structures that you will encounter:
See the two diagrams below where White has three pawns in the center.
On the left diagram he pushed the f,e and d pawns into the center to gain control over center squares.
On the right diagram he pushed the e,d and c pawns, not the f-pawn.
Yes, if the f-pawn is pushed (see left diagram) there is a weakness near the kingside because the diagonal h4-e1 is weakened. You could give a check on h4 with your queen. I don't say Black should do this. I just say there are some variations where this can be done. This does not necessarily mean that Black gets an advantage giving a check by Qh4+, but this possibilty exists and can be used.
In both structures the white e-pawn is under pressure and Black should give attention to e4 in any case, as the bishop b7 is directed to e4 and this is where the action is. This is the reason why Black plays f5 to add pressure to e4.
In the right diagram below playing the e,d,c set up, White cannot capture the f-pawn because Black will hit g2 playing Bxg2 and wins a rook after that. After this Black has advantage. White will get an attack going, but this attack is weak.
For example (right diagram) 1.exf5 Bxg2 2.Qh5+ but the black king will retreat safely to f8 and then Black develops further playing Nf6 attacking the queen and gaining time to recover. After this Black should win.
Black moves White moves (not 1.exf5? Bxg2!)