Death132: Are all GOG games up to date with the current game version with all of the patches?
Do you mean the GOG patches, or the patches out there in the internet? Either way it's a broad statement. If a GOG game has GOG patches, the installer is NOT patched. Nevertheless, some games from before the era of GOG patches are patched instead, because they had no other way of distributing the patches
As for patches out on the internet, who can say? Often yes. Sometimes no, because GOG introduced fixes that aren't compatible with a patch, (sometimes because GOG's fixes were better for modern machines) but that's rare. Sometimes no, just because. Fan patches are included more or less never, but I think Dungeon Keeper 2's GOG Patch involves similar fixes to a fan patch and for all I know might include it.
Sometimes the games' description will mention a patch, but not always.
The situations can be so varied you'd be better off asking game-for-game in the respective forums, or searching the forum for posts on the subject.