Linking your Facebook account to your game will ensure that your progress will be saved even if you need to delete the application or switch devices.
However, there are two important things we ask you to note:
If you need to delete KINGDOM HEARTS Unchained χ, make sure you are logged into Facebook within the game before deleting. If you delete the application while logged out of Facebook, you will be unable to restore your data even after reinstalling the game.
When re-installing the game, if you wish to migrate your old data, please make sure that you select "Migrate Data" when prompted to during the installation. If you mistakenly chose to start a new game during installation, please delete the application, re-download it, and select “Migrate Data” during installation.