Is forcing ATV 4 into hibernation/shut down possible?
Unfortunately no. There is no known way (protocol wise) of doing this.
Okay Thanks. I guess not much is possible then. Pausing a movie in the Plex app does not work either and showing metadata from different apps also not.
Pausing in plex is a known issue with the media player in tvOS (there’s a link here: https://github.com/postlund/pyatv/blob/master/docs/faq.rst). Regarding metadata, this is something that is also known and being troubleshooted in another thread. Not sure what the issue is yet, but the DAAP-support on the ATV4 does not seem to be great. My goal is to reverse engineer the MediaRemote framework, but as I only own a gen 3 device I’m not able to do that. Waiting for gen 5.
Could be great if the possibilities would increase in the future.
-Is it also not possible to get the on/off(standby) State of the Apple tv?
-is it possible to get info what app is currently loaded/running?
I would like to know This for some automation for my hyperion light.
No, there’s not a known way to figure that out. It’s one of the most common question 
When you make a request to the device, any request, it will wake up. It’s just how it’s designed.
The DAAP protocol was designed around media, like music and video and has no notion of apps. So it’s not possible to know which app is running either. It may be possible with the MediaRemote protocol but I don’t know. Once I have a device and some time I will try to figure that out.