Going against the grain here...

SSJ2 Gohan would lose to Android 17 and 18.

This is because:

A. In the History of Trunks manga, Android 17 claimed that he hadn't even used 50% of his power against Gohan before. Despite beating him every time.

B. The general consensus and official guidebook state that the SSJ2 multiplier is 2x SSJ1.

Hence, simple math shows that Android 17 would still have the power advantage against SSJ2 Gohan. Add Android 18 into the mix, and the fact that they have infinite energy/stamina... Gohan stands extremely little chance.

SSJ2 Future Gohan is not even remotely close to the SSJ2 Gohan who defeated Cell. In the same sense that the SSJ2 Gohan who defeated Cell is not even remotely close to current SSJ2 Goku (previous base Goku was shown to far exceed SSJ3 Gotenks for example).

Future Gohan is very weak. He got constantly beaten by Android 17/18 who never even went to 50% power. Trunks also stated that the future androids were weaker than the present ones. If Trunks was right, then that makes Gohan even weaker.

Without SSJ2, I'm not even sure if he'd beat Mecha Frieza & King Cold to be honest. Even with it, he isn't beating the androids or Imperfect Cell.

He made very little progress in 14 years. He has 0 chance of preparing for Dabura, Buu, Zamasu, or anyone else.