This TuT will work only for iOS.
1. Delete your account on Facebook in Settings.
2. Log out your account in the Facebook App !
3. Open brave frontier, press agree and don't press anything on the screen !
4. Tap and hold for 15 seconds the uppermost part of the screen.
5. This will reset the saved accounts in your Brave Frontier.
6. Login your another Facebook account in the Facebook App.
7. Play Brave Frontier and Login via Fb.
Will provide screenshots lateeer if I have the time.