If you didn't try and don't understand what the app does then you should not post anything....
yep, you are right, I shouldn't have said anything. "reboot update" gave me the impression, that it would just reboot, after an update. ie after copying a new update into the update folder.
I have now tried it on my S912, & yes indeed it does get into the recovery mode.
So, I now consider myself, castigated.