Does anybody know if it’s possible to emergency stop and restart a mini 3 pro mid air?

  

Hi there, you can refer to the methods below.
1. Go to “Safety“ and “Advanced Settings” in DJI Fly, and then set “Emergency Propeller Stop” to “Anytime”. Then during flight, keep pushing both control sticks to the inner or outer corners for 1.5s to stop the motors.
2. Go to “Safety” and ”Advanced Settings” in DJI Fly, and then set “Emergency Propeller Stop” to “Emergency Only”. Then during flight, when the flight controller determines that there is an error with the aircraft, keep pushing both control sticks to the inner or outer corners for 1.5s and the motors can stop.

I don't think it is possible.  If memory serves me right you could do it with the Mavic Pro but no drone since that I know of.