When does the velocity and speed of a moving body become identical?

Velocity and speed are never identical. Velocity is a vector quantity. It takes two numbers to describe a velocity. One number for its size the other number for its direction. Speed is a scalar quantity. It only has size and only needs one number to describe it. The size of a vector may be identical to a speed. But the two quantities are never completely identical.

Velocity and speed of a moving body become identical when it tends to move in a straight line.