none and i repeat none of the FF worlds are the same world except for a couple within their own canon... only Gaia from the FFVII Compilation, Spira from FFX project, & Ivalice from any game by the Ivalice Alliance are consistant with other games but only within their own canon... each numbered game is not a sequal of the prior some billion years later, they are each their own worlds within the FF universe, but the creators did leave a few leading hints that they are all within the same universe though...