So much for cheesing the speed run achievements. LOL
There's still co-op. That's pretty much cheesing them in the eyes of the hardcore speedrunning community.
Then there's Blastermaster for the Halo 2 speedrun, aka Bandanna but still allowed.
They're gonna be totally doable for most veteran Halo fans unless you're like my buddy and suck horribly without KB+M.
Is H2A and H2 two different games? If so is there differences in achievements and stuff?
I assumed A was just an up ressed version of the original.
Halo 2 Anniversary IS Halo 2 in this collection. You can either play it in classic mode, or you can hit the 'windows' button on your XB1 controller to switch to Anniversary mode.
Anniversary mode isn't just up-rezzed. It is a completely remastered layer over the original that retouches all the assets, artwork, textures, skyboxes, etc. It also has completely re-done cinematics, this time in CG rather than using the game engine.
As far as achievements, there are some that are in classic mode (lots of easter eggs specifically), some that are in Anniversary mode (terminals, toy plushy dolls), and some that are both (completing campaign having viewed every level in both classic and remastered).
As for multiplayer, there is Halo 2 classic, which is just up-rezzed ports of all the original maps and gameplay that you remember, but in 1080p/60fps.
Then there is Halo 2 Anniversary multiplayer, which is 6 maps that have been re-done in a modified Halo 4 engine in an attempt to retain as much of their original gameplay character as possible, while also adding in a few new flourishes (dynamic things on the map) and heftily remastered visuals.
As far as achievement here are concerned, once again there are achievements tied to H2 classic multiplayer, as well as a LOT of achievements tied to H2 Anniversary multiplayer.
My achievement guide/walkthrough on TrueAchievements is 99% complete. I'm only missing 2 of the 4 chips dubbo achievement locations (H3 and H4) as well as 2 other random ones. As soon as it is published on TA I will be linking it here and hopefully petitioning to add it to the OP.