8.3 keeps crashing my ipad when using my apps

I have the first Ipad AIR ...

Ever since I installed the new operating system update... 8.03 it keeps shutting down a lot of my apps when I am on them . I hate this! It happens right in the middle of when I am doing something. Can I fix this problem somehow , or can I go back to previous operating systems? It also keeps telling me my password for my mail is wrong. But I still get the mail because it's not . How can I get rid of this message popping up?

Thank you