how to enable shutdown the whole device from kodi app??

I didn't think Kodi ever had the option to shutdown an Android-based device. However, there were some custom forks that had that as an option, as I remember. Maybe that is what your friend is running.

If you have a rooted device, you could choose a Kodi shutdown (in say, 1 hour) in tandem with an Android device shutdown -- via app -- (in say 1 hour 5 min).

Possibly someone can chime in with more sage advice.