Conjunction of tactical methods

not bad 

What if white plays 4. Qd1?

4... e5 5. Re3 then what?

This is not a forcing combination. This is not even a tactic.

At most 1... Bxd4 2. Rxd4 2... f6 is the best continuation for black that gives no clear advantage in a complicated position.

First, in the opening of Sicillian-Four Knights Variation, it's been theorectically wrong for white to play long castling (you can play it, but it's not a good variation) and white won't be able to really gain materia or real advantage; for this theory, you can check it out on proffesional chess opening books or test it on your laptop(if you got proffesional chess software). By the way, if black does not wanna catch a possible chance to get materia from white, it's been theorectically correct for black to play f5; if white does not play ef, white won't be able to really attack the black king(you can try to play white side of this game on your laptop) and black will start to attack the side of line a、b and c by play the methods showed below, as the same as responding white play Qd1、Re3. 

 It's true that white won't lose material if he plays as you say, but white does lose initiative and it will be pretty good for black to attack the white king; he can focus that on line C or play 1...Nc4 2.Bc4 bc to open the line B, or he can directly sacrifices his pawn on line a and b to attack the white king. Anyway, this will also be bad for white to play.

I didn't say in the post that black must gain materia(the only force move I say is that white have to play ef after black plays f6), but whatever white play after 1.Bd4 Rd4 2.f6, black will either gain materia or get the initiative.

And Shoppi, thanks for showing your positive opinions on this game. In fact, it's a game played by my teammates and has been commented by our couch; next time, I gonna ask him about the best variation for black if white plays as what you say.

You bring up good points and interesting ideas. I was just pointing out the fact that this is still a game in progress and can really go either way

As for the conventional puzzle, there is usually a forced combination that gives material or a winning advantage. That of course does not exist here. Like I said, the first two moves really look best for black to try and seize the initiative, but after that there are too many options to consider =)