Any special instructions to uninstall itunes 12.2 go back to 12.0.1.26?

See turingtest2's user tip on Troubleshooting issues with iTunes for Windows updates for details of the steps that may be needed to completely remove all components of a previous iTunes installation before installing a new one.

Note also that if you've run either of the 12.2 releases your iTunes database will have been updated and won't be compatible with 12.0. To address this, you'll need to locate the dated version of the iTunes Library.itl file in your Previous iTunes Libraries folder that corresponds to an update from 12.0 or 12.1 to a later version. For example, if you installed 12.2.0 on its day of release you should find a file called iTunes Library 2015-06-30.itl. Then (with iTunes not running):

• Locate your current iTunes database (the active iTunes Library.itl - by default in C:\Users\username\Music\iTunes)
• Move or rename this file.
• Copy the appropriate dated library file from the Previous iTunes Libraries folder to the iTunes folder.
• Renaming this file iTunes Library.itl

Once you've installed and run iTunes 12.0 it will be able to open the restored database file. Note, however, that the contents of your library will now be as they were when the restore library file was copied to Previous iTunes Libraries; any additions or changes you've made since that date will not be available.

Before starting you should take a complete backup of your current library so that you can restore it's current state in case of any issues occurring during the rollback process. See Backup your iTunes for Windows library with SyncToy for a recommended method.