Sicilian Alapin versus Sicilian Delayed Alapin

You will definitely snare some people who don't know their lines that way, but much easier for Black is just 4...Nc6, then your e-pawn actually is hanging and there's nothing better than 5. d3, which transposes into a line more usually reached via 1. e4 c5 2. Nf3 d6 3. Bc4 Nf6 4. d3 Nc6 5. c3. I don't know if that line actually has a name. I call it the Delayed Bowdler. It's fine for White but just an equal quiet line.

4...Nc6 just falls into white's main idea (which is not robbing a piece from a noob opponent).

5.d4! is the right reaction, when it is extremely dangerous for Black to grab the pawn (actually in the main line Black can grab three pawns).

Against 1... d6 the delayed alapin is terrible, since black can play Nf6 and pressure the pawn, but you can't push e5 now. Of course, if black does take the pawn you have Qa4+ check picking up the knight. But you also have no good way of defending e4... so black can just fiancetto or guard himself from the check, and eventually you'll be forced to defend the pawn. But as a result you can't push d4 without waiting / making major concessions, since the moment you do... the pawn drops. And moves like Qc2 don't secure d4 due Qc7 threatening the queen. So overall you're actually forced to make some major concession - either d3, Bd3 > Bc2, or O-O > Re1 > Bf1... and you have no advantage to speak of -

Against 1... Nc6 or 1... e6 you'll often get the same position you would have gotten in the mainline Alapin. The advantage here I suppose would be it allows you to pick and choose which alapin lines you want to play.

But I'd play it against Nc6 / e6 and against d6 I'd either learn the Chekhover, or the Prins, or really just play the open lines is probably what I'd do.

I must admit I have not seen this before (d4 is played 8% of the time there at Lichess 2000+) and it looks a little hairy. Maybe I should just play 4...e6 instead.

4...g6 is the most played move, followed by 4...Nbd7.