LogFAQs > #972417196

I haven't really played MH since Freedom 2 and never actually beat it, so I'm probably in no position to answer but I get the general impression that MH games get a bit easier/more accessible with each game (although there's not too much difference either until you get to World and Rise).

I think Generations is more of a "best of" game, with monsters from across the series. But 3 and 4 are the "G/ultimate" versions while Generations is not (as it's on the Switch). This means that it doesn't have the postgame level G rank quests that get added in the G/Ultimate rereleases although if you're just planning on doing the elder/story quests and then you probably won't get to that point (guild quests have enemies with higher hp because they're balanced more with multiplayer in mind, you can still play them solo I think they'd just be a lot more damage spongy solo).

I think all the MH DLC is free? But it's probably mostly just quests for high level players.

You might have some trouble playing on a regular 3ds without the new 3ds' c stick nub because of the camera control, although I guess there's a circle pad attachment for the regular 3ds.