1) It is foolish to rely on FR24, the sytem works by collecting data over the internet from amatuer ADSB receivers owned by enthusiasts and joining the dots. There are plenty of these stations in well populated areas but the chances of any reliable receiver data in the middle of an enormous desert are a tad slim. In these circumstances FR24 extrapolates (guesses) by extending the last known trajectory until it recieves a valid report or times out.
Do they extrapolate? A line showing heading is displayed but the data used is of two types. The data actually transmitted by the aircraft and a position triangulated from several receiving points of the aircraft's radio transmissions.