(A) : A body is momentarily at rest at the instant it reverses the direction.
(R) : A body cannot have acceleration if its velocity is zero at a given instant of time.

To reverse the direction of motion, the velocity of the body become zero at the instant and then becomes negative of the previous.

If the velocity is zero at an instant, the acceleration need not be zero at that instant. The velocity at height point for a vertically projected body is zero but acceleration is equal to acceleration due to gravity.