The 3.1 series is the first based on the new netcode, with new terrain renderer and many other changes. The main target are systems capable of OpenGL 2.0 (with shaders), but at least the important things like team colours should work with OpenGL 1.4+ (some things might look strange though).
Configuration uses a new directory, if you want to use old mods/maps/savegames, you need to copy them (see FileLocations
). Note that savegames from 2.3 and 3.0 are incompatible, only those from newer master snapshots might still work. For mods it depends on what they do, don't expect old mods to work either.
2.3 is now officially unsupported.