If you have a guest account and login to a new Facebook account - not previously connected with Paint it!- this means you will be making an Upgrade to a Facebook Connected account. All your progress will be transferred from your guest account to your Facebook account. Your guest account is now a Facebook Connected account. The unique ID is the same.
With an Upgrade, if you logout from Facebook you will be directed to a login screen again and be able to choose if you want to log in as a guest or with a Facebook account. If you decide to login with guest, then a new Guest user will be created with zero progress.
Logging in with a Pre-existing Facebook Connected Account
If you have a guest account with progress already made, and you decide to log in to an old Facebook account (that was already logged in Paint it! game), a pop-up will appear warning your guest account has a different progress than your previous Facebook account. You will need to choose which account you want to maintain active.
If you choose the existing Facebook account, since this is not an upgrade your guest account will be saved in our game server. This means once you log out from Facebook you will return to your old guest account with its specific progress.