[Porsche-O-Phile]

I've flown lots of airplanes (including twins) that had knots or mph as the airspeed indication.

Yes, a twin can fly inverted... briefly. As in "rolling". So I've been told.

Leaving your mobile phone on in an aircraft is a violation of FCC regulations (or used to be, maybe it's different now). It also would tend to kill the battery pretty quickly since the phone would be tripping into "high power / roaming" mode to try to maintain connectivity the further away from the towers / network (higher up) you get.