Warning: If you start playing as a guest for 2 hours without linking, then finally link your Facebook, the game might ask: "Which save do you want to keep?" If you accidentally choose the 2-hour guest save over your 2-year cloud save, you overwrite your progress. Fix: This is recoverable if you act fast. Uninstall the game immediately. Reinstall and log into Facebook before the app loads any data. The cloud save should still exist.
If you want 99.9% safety for your Angry Birds 2 data, use the "Double Link" strategy. angry birds 2 save data link
Why? If Facebook goes down (which happens), your Google/Apple link still works. If you switch from iPhone to Android, Facebook is the only universal translator. By having both active, you create a failsafe. To check if you are double-linked: Wait 2–5 days for manual transfer