Even for the off-beat and unusual Jerome Gambit (1.e4 e5 2.Bc4 Nc6 3.Nf3 Bc5 4.Bxf7+) there is a certain amount of "theory" that is good to know, to guide your way through the complications. Especially Black would benefit from an understanding about what he is getting himself into when he plays 6...g6 in response to White's Queen sally 5.Qh5+; like it or not, it is a tacit offer of a Rook, and he has to be aware of that and deal with it. Otherwise, problems like in the following game will crop up.
Anonymous - Anonymous
10 0 blitz, Chess.com, 2020
1.e4 e5 2.Bc4 Nc6 3.Nf3 Bc5 4.Bxf7+
4...Kxf7 5.Nxe5+ Nxe5 6.Qh5+ g6 7.Qxe5
7...Bd6
I was surprised to find 50 games with this move in The Database, but I was not surprised to find that White scores 89% against it.
It is true that 7...Bd6 saves Black's Bishop, but it does nothing about the threat to the Rook at h8. That is the challenge when Black plays 6...g6: it is fun to kick the enemy Queen with a pawn, but what about the Rook?
Blackburne's Defense, 7...d6, says Go ahead and take the Rook, I will trap your Queen and checkmate your King. It doesn't always work out that way - in fact, The Database has 911 games with the move, and White scores 70% - because players can get lost in the complications, but Black needs to know, beforehand, what he is getting into.
Whistler's Defense, 7...Qe7, says Go ahead and take the Rook, I am aiming at your King. Again, probably because White is more experienced with the Jerome Gambit - and that helps in a complicated positions - The Database gives 576 games with 7...Qe7, with White scoring 64%. Black's best chances come after he sacrifices the Rook.
So, the warning is - be aware, defenders, that 6...g6 means you want to sacrifice your Rook. Play becomes awkward without this awareness.
8.Qxh8 b6
Also seen recently:
8...Qe7 9.Qxh7+ Kf8 10.Qxg6 Qg7 11.Qf5+ Nf6 12.0–0 Bxh2+ 13.Kxh2 d6 14.Qf4 Qh7+ 15.Kg1 Ke7 16.Re1 Nh5 17.Qg5+ Ke8 18.Nc3 Black resigned, Unjana - indBasher, 5 8 blitz, lichess.org, 2020; and
8...Qh4 9.Qd4 Nf6 10.g3 Qg5 11.d3 b6 12.Bxg5 Black resigned, soraneptune - akainth07, 3 0 blitz, Chess.com, 2020.
9.b3
Simplest is 9.Qxh7+, making sure that the Queen will not be trapped, but White is confident that she will be safe.
9...Bb7 10.Bb2 Bxe4
White is up the exchange and a pawn, but he is most happy about his control (and threats) along the a1-h8 diagonal.
11.Qg7+ Ke8 12.Qxg8+ Bf8 13.O-O Bxc2
Grabbing a pawn, as there is not much else to do. He could have tried 13...Qg5, threatening mate, but after 14.g3 Qf5 (hoping to come to f3) White had 15.Nc3, threatening to snap off the Bishop, and, after 15...Bb7, he could turn from defense to attack with 16.Rae1+. (He can keep Black's Queen out of f3 with f2-f4.)
14.Re1+
Crushing.
14...Qe7 15.Rxe7+ Kxe7 16.Bg7
You knew that move was coming, right?
16...Bxg7 17.Qxg7+ Kd6 18.Qd4+ Kc6 19.Qc3+ Kb7 20.Qxc2 Re8 21.Nc3 Black resigned
The material loss is too much to continue with.