There are a couple of caveats to keep in mind before doing anything:
Backup your data first! Not that you had no excuse not anyway, but make sure to back up your data before upgrading if you have something that can not be recovered. Or even if it does not. Just do a backup.
You will not be able to use the recovery partition to downgrade. If you have a recovery partition on the system, which will no longer be able to restore your computer to the Windows version you had before.
Recovery will support external Rollback. As is expected, since it has a recovery partition, you need a floppy or USB with Windows 8 (or more) on it to go back to how things were, if you do not like or can not use Windows 10."
Link to Original Source