Question

Is initial velocity and final velocity instantaneous?

Answer 1

Yes initial and final velocity are instantaneous because initial velocity is the measure of the body when the body is at rest or in motion and final velocity is the velocity of the body at the end of the displacement.

Answer 2

If the graph is not a straight line (i.e., a curve) then the slope of that curve's tangent line at some specific time is equal to the object's instantaneous velocity. ... If an object goes from an initial velocity to a final velocity, undergoing constant acceleration, you can simply "average" the two velocities this way.