You can basically copy all of the folders from your old Dolphin folder and put them in the one for the latest revision. Or just download the latest revision, and replace the .exe file in your old Dolphin folder. Either way is up to you.
Dolphin emulates a large majority of GC and Wii games, perfectly or with minor to moderate inaccuracies (a lot are fixable with the right settings, some aren't though). Only a handful of games are truly broken atm. A lot of Virtual Console games should work, but frankly we have far too few people reporting about them (at least judging from the wiki). Dolphin can also play WiiWare, and some homebrew I assume.
Dolphin emulates a large majority of GC and Wii games, perfectly or with minor to moderate inaccuracies (a lot are fixable with the right settings, some aren't though). Only a handful of games are truly broken atm. A lot of Virtual Console games should work, but frankly we have far too few people reporting about them (at least judging from the wiki). Dolphin can also play WiiWare, and some homebrew I assume.