No OTAs will stay and you can always revert to original state fairly easy with this phone. Clockword is a recovery partition that overwrites the original anrdoid recovery. This allows you to modify system files, flash roms, wipe cache and davlik. So the way it works is phone first boots bootloader and from bootloader you have an option to boot either recovery or android OS. usually you have to enter bootloader manually via hardware key combo or via adb.