Answer : Thyristor can be turn on by positive gate pulse and the current will continue to flow through the device even when the gate voltage is low hence thyristor is called latching device.
Answer : already answered here is mosfet current controlled device?
Answer : No, IGBT is not the current controlled device. IGBT is a voltage controlled device. IGBT have combine qualities of MOSFET and BJT. The high switching speed of MOSFET and low conduction losses of BJT. Also, IGBT which stands for Insulated Gate Bipolar Transistor have high input impedance.
Answer : No, BJT is a current controlled device .
Answer : MOSFET are voltage controlled devices.