The transmission shifter will only slide into Neutral, but never in reverse. I've actually TRIED that during test drive, to make sure passenger can not accidentally cause this.

I did not try to push the ON/OFF button; my guesstimate that it will do nothing to the engine (it may throw some warning indicator/tone, at the most).

__________________
His : 2013 X5 3.5d Deep Sea Blue/Black/Aluminum with ALL packages, 20" 214"s, running boards, Adaptive Drive, Spare Tire, BMW Apps
On Order : 2016 X3 3.5 MSport Silver/Mocha with DHP, CW, Prem, Tech, DA, Lighting

Hers : 2015 328xi MSport Silver/Red

Prior:
2008 X5 4.8
2011 X5 3.5d
2010 335 xDrive
2013 335 xDrive