FAA Regulation

No higher than 200 feet. No higher than 400 feet. No higher than 300 feet.

The National Transportation Safety Board. Upon request of the Federal Aviation Administration.  Air Traffic Control.

No more than three as long as the Remote PIC maintains visual line of sight. As many as he/she can handle. No more than one. 

It must not contain exposed rotating parts that can lacerate.  It must not contain exposed rotating parts that can lacerate and must not cause injury equivalent to 11 ft-lb of kinetic energy.

No Medical Certificates are required. A Class 3 Medical Certificate A Class 2 Medical Certificate.

the Remote PIC.  the controlling agency. Air Traffic Control.

If prior permission is received from the Federal Aviation Administration. If precautions are taken to avoid injury or damage to persons or property on the surface.  Only in an emergency.

Compliant with Part 107. Part 107 does not apply to this scenario. Not compliant with Part 107.