Fake crash is described in the protocol, either pothole or speed check and drivers usually press on the brakes so that traffic enforcement camera would not take a picture of the vehicle and would not get fined.
Limited crash trace is sent when Crash trace setting has "Trace Changes" setting enabled. It is GNSS and acceleration data, when acceleration values are changed by more then 50mG
While Trace Full sample's all the data during crash and generates more data as a result.
Real crash - it is opposite of fake crash, when threshold was reached and it is detected as a real crash. Detection is done internally on the device, you do not need to worry about configuring it.
Regarding Crash detection you can find more information on our WIki: https://wiki.teltonika-gps.com/view/FMB202_Accelerometer_Features_settings#Crash_Detection