I would like to downgrade to one of the previous versions of Parallels Desktop.
Is there a chance I lose some data in Windows after the downgrade?
Do I have to uninstall the current version first, then downgrade?
By downgrading Parallels Desktop nothing in Windows virtual machine will be affected at all. All applications and data will stay in the same condition and place you left it before downgrading.
NOTE: Nevertheless, we strongly recommend to shut down Windows (Actions > Shut Down) before downgrading and back up your Windows virtual machine.
There is no need to uninstall the current version of Parallels Desktop before downgrading, just launch the installer of the previous version. It will completely replace the existing one.
When the downgrade is complete, start your Windows virtual machine, then wait for Parallels Tools to update and restart Windows.
If you wish to upgrade Parallels Desktop to the newer version, just download and launch the installer using the links below:
Parallels Desktop 13: Download
Parallels Desktop 12: Download