I haven't tired this yet but maybe it will work for you.
1) Open Angry Birds then press play button
2) Select an area you haven't unlocked yet. (Mighty Hoax, Danger Above, The Big Setup, Ham 'em High)
3) Quickly press back button then home button.
4) Swipe card up and away.
5) Open Angry Birds again and quickly tap "Play" repeatedly.
6) If you did it correctly, you should be in the locked "world" with 1st level.
7) Make sure to get any amount of stars on the first level, else when you back out the world will still be locked.