Android Question Screen facing up or facing down

That will depend on the device, if it has a proximity sensor (usually next to the front facing camera)

Thank you @NJDude , thank you for the reply.
I basically need it to work on all devices with the screen is powered off but the device is physically on(or in stand by mode).

It's mainly for myself, I just need it to control one or two phone features on my business mobile when the screen is faced downwards.

You could try the other sensors, I haven't tried that myself so you will have to test it yourself, not sure how accurate that would be.

The ORIENTATION sensor set in between 4 values worked a treat @NJDude, thank you...