Coverage depends on ground receiver reception and is not a complete picture of traffic.
The hex code is the aircraft's ICAO 24-bit address, broadcast by its ADS-B transponder. It is the key used to match live position reports to this registration.
The pilot's loss of airplane control during a low-altitude aerobatic maneuver.
The pilot of the other airplane not following the instructions briefed by the formation leader, and clearance not maintained by the pilot of the other airplane. A factor relating to this accident was the area of restricted visibility in front of the pilot of the other airplane when the airplane sits on its tailwheel.