Roll back from OS X Mavericks ( or any newer OS) to Mountain Lion I installed the developer preview of OS X Mavericks, &amp; too many things broke. I can't stay on it &amp; need to roll back to Mountain Lion. Any ways of doing that? Please help!

I originally installed Mountain Lion &amp; Mavericks through the Mac App Store.
Since the question does not mention backups, I guess there aren't any.  What you can try in this case, is to make a time machine backup (e.g. on an external USB Harddrive) of the current Mavericks partition. 

Then do a clean install (as suggested by jaume) and then use the migration assistant getting your data back from the Maverick backup into Mountain Lion.