i still searching employer for doing my project too lets see what will happen next..
If somebody is interested in the gameboy phone they can contact me by email firstname.lastname@example.org
First i couldnt use the phone to call when it was closed.
Then i used the app Fullscreen Caller ID and i could use the phone to call when its closed .
With fully functional front and backspeaker but the mic is underneath the display when its closed.