In order to enter the game for the first time and start playing, you'll need a Facebook or an email account.
The game information, as well as statistics and purchases, are associated with the account. This is why you can't change the email address, since all of your achievements would be lost.
If you sign in using the wrong information, the player's information may not be displayed. If this were to happen, we recommend you sign out and try again.
If you created your account using en email address, you can choose to link it with Facebook later. In order to do this, you'll need to go to Options, Account and once you're there, in the Facebook option, tap on "Connect".
You'll also be able to unlink it, but an email address must be associated with your account.