Velocity is a quantity that has magnitude as well as direction so it can be negative and positive but the speed is a quantity that does not have any direction but has magnitude, there is no chance of getting negative. so the speed is always positive. so velocity can never be greater than the speed (maximum it can be equal to the speed if it travel in a straight line where direction does not matters )
Because speed is distance upon time and velocity is displacement upon time
and displacement can never be greater than distance so velocity can never be greater than speed.
Remaining options are true .
Speedometer reads speed at an instant. Position -time graph for variable speed is a curve because speed (slope of position -time graph) is changing.
And velocity-time graph for uniform motion will be horizontal line parallel to time-axis as velocity is fixed and does not change with time.