First problem is of GATE 2014. This problem is on determination of input impedance when terminated by complex load.
Second problem is based on transient response of line which is terminated by resistive load. The unknown load resistance is to be determined. Bounce diagram is the convenient tool to solve such problems.
Third problem is of GATE 2016. It has two cascaded sections of lines. Input reflection coefficient is given. Length of unknown line section is to be determined.