Birth by Sleep Final Episode question(s)

I'm trying to play through proud mode to get to the Final Episode. I've watched videos on Youtube to prepare for it, but I read a description saying that the Land of Departure, which contains the mysterious figure, isn't accessible. I don't understand this. I want to try and defeat both Vanitas's lingering spirit and the mysterious figure, can someone explain how I get to those parts and any advice? Thanks :)

 

Once you create a save file after completing the final episode, reload an old saved file (either terra ven or aqua) go to keyblade graveyard and vanitas S. Should be there.Defeating him will allow you to fight mysterious figure in land of departure. And for a tip when fighting vanitas lingering spirit with Ventus, use the command Tornado. That really takes alot of HP from him

 

Thank you!