Unable to open old installations

I have an old world that was last used on 1.4.2, and I was attempting to open it in 1.4.4. However, the April Fools snapshot messed up my game and I am unable to open any past installations other than the latest release and the Fools snapshot. I have put in a ton of work into my worlds and I am unable to open them because of this snapshot. My username is Mwlithea.