Please correct me if I'm wrong, you already have an acc which has linked to a fb acc, but still you fail to load this save with the mod apk ver. 5.2.2 because the app keep telling you to upgrade rather than has the usual "Later" option? All in one device.
If you've started a new game with the mod apk (already past the character settings window), you have to delete/reset your game data through in-game settings and that will get you back to the character settings window. Close the game, uninstall the current mod apk, and then install mod ver. 5.2.2. Do the steps again from the beginning. If it still doesn't work, you might have to use the unsigned one. Though, it requires you to root your device and patch it again with the Lucky Patcher. Because with the fb bind nowadays, we can't start a new game with mod apk. You have to make a new game account through vanilla version, bind your acc to fb and by then you can use the 5.2.2 trick.
I don't know where the save file for the game is located since I don't typically dabble with it. I've had my account forced-log-out in the past, even I recently synced up to another device, I have no problem whatsoever with this guide.