8. Qd2 or 8. f3 in the English Attack?
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I think you should be able to play either (and, I imagine that, on move 9, you'll probably play the other move anyway in most cases, unless Black does something that calls for a different response).
If what you're asking is whether, upon Qd2, Black can play Ng5, remember that you still have Bg5 in response (and on f6 you can always go to h4...if Black continues weakening with g5 I don't know how he'll survive that game, and it's not really clear what he's accomplished with all that).
I suppose that Qd2 is slightly more flexible as well, because you haven't committed to weaking the dark-square diagonal on the Kingside yet, just in the off chance that Black does something that makes you decide to castle short (I'm not quite sure what line that would be though, as you'll probably go long on almost anything).
Just my thoughts of course, perhaps wait on some experts in the English attack and/or check an engine to see if Black has something in either variation that would reduce your advantage.
Seems to make almost no difference as far as I can tell, since 8. Qd2 Ng4? doesn't make sense for black. They should transpose.
definitely c4.
Some ideas I could gather
(A) Allows another opportunity for a draw if Ng4 is played (White plays Bg5, Black plays the knight back to f6, and White plays back with Be3. Other moves by Black probably give White a slight advantage.
(B) Allows White to castle earlier. Not sure if this option is useful.
(C) Allows the option of playing f4 without losing a tempo. Again not sure if this option is useful. Perhaps the idea is to either (1) isolate the d-pawn if Black captures on f4 or (2) more or less, force Black to capture the knight on b3 after the move f5 (otherwise the bishop becomes passive). Since the key square is d5 there has got to be some use in getting rid of Black's light-squared bishop.
(D) Perhaps it confuses lower-rated players who are playing as Black. But this can't be that useful because if he continues with his usual moves, then he will be fine.
