We've been separately developing/customizing SugarCRM OS ver 4.0.0beta.

Many of the customizations are bugs addressed in teh many versions since.
But many are not. Is it possible to upgrade at this point? Will we lose all our
changes not present in the lastest version?

Or would it be best to start from scratch with a fresh install, sort out all changes
not in the new version and add them again?

Thanks,
Rey