First, it was working with the release and stopped working when you installed the beta. Beta software is often buggy. Installing Parallels betas often requires installing a new version of tools which will be incompatible with the previous release so the only way to go back is to uninstall the tools or restore a backup.
If you start over, with the release version, and once you get it working, back up your VM (use Finder), there's no need to travel with installation disks, and if you install something that causes it to stop working, you can restore the backup (after reverting the app if necessary).
My backups have saved me countless hours when things didn't go as expected. Any time you touch a machine, there's at least a mall risk something will go wrong. If you don't have backups, eventually you will get bitten. It may take a while, but it will happen.