Full list of all 20 Angry Birds Classic achievements worth 200 gamerscore. It takes around 40-50 hours to unlock all of the achievements on Windows Phone.
All achievements
Achievements they've won
Achievements they've not won
Collect three stars in all levels of the episode
Collect Secret Cake
Play Angry Birds for 30 hours
Shoot 5,000 birds
Play Angry Birds for 15 hours
Play Angry Birds for 5 hours
Unlock Boomerang bird
Unlock Big Brother bird
Unlock White bird
Unlock Black bird
Unlock Yellow bird
Unlock Blue bird