Multiple issues

Ever since 1.6 came out there have been multiple issues.

1. I lost the ability to enter any of my worlds that were created before 1.6. The game just crashes when you try to enter it.
2. i started new worlds (survival) and they too become inaccessible shortly after the game glitches and crashes.
3. the Movement will work just fine, then all of a sudden it will jump 90% vertically. This causes some interesting experiences when fighting a baby zombie.
4. more and more frequently the game will just minimize for no reason.

I really want access to one of my worlds since I finally got a top level fishing pole and bow