Larian Studios Forums Divinity - Original Sin Divinity - Original Sin - General Talents that can be replaced or changed

You can make a copy of the install folder, or otherwise back up the current version of the game. The next update will be "some months", though, so that may not be necessary. You would be able to start the game directly from the executable, though wouldn't have Steamworks features that way (achievement and playtime tracking, the online lobby and Steam friends invite function for co-op).