Black's 4th move is utter crap!
is this playable openning?
Black's 4th move is utter crap!
how to exploit that move?
Look at the position before move 1:
both sides have no pawns in the center. Both sides have no pieces developed.
Look at the position after black's move 6:
White has more central space (pawn on 4th rank). White's queen is developed and none of black's pieces are.

Yeah, there's no point to 6.Bf4. Your Queen is centralized, and Black no longer has that knight to kick it. If you are White in that position after move 5, you should be thrilled! If you are Black in that position after move 5, take up Tic Tac Toe instead!
Play normal moves and maintain your lead in development. Just because Black did something stupid doesn't mean it's time to blow up the Black King in 10 moves or less. This is not "big-a-move" (in reference to "bid-a-note" on the 80's gameshow, Name that Tune). It's not about how few moves you can mate black in. It's about winning the game. I've won games that have gone into the triple digits before!
I used to play this openning.
this openning have been playable given me easy win when black didnt choose 8 Qe5+ Qe7