A body, whose momentum is constant, must have constant

A body whose speed is constant :

Does a body moving around a circular path with constant speed have constant velocity? Give reasons.

How much force acts on a body whose momentum is constant

A body is moving such that its linear momentum remains constant. Is the body in equilibrium?

A body whose speed in a particular direction is constant

Can a body have energy without having momentum. Can a body have momentum without having energy ? Explain .