(a) No. The potential difference is a field property. Potential energy is the interaction energy of charge configuration.
(b) The electrostatic potential at a point in an electric field is defined as the work done in bringing a unit positive charge from infinity to that point against the field. The electric potential difference between the two points is equal to the work done in moving a unit test charge between them. The potential energy of a system of charges is defined as the work done in bringing the charges from infinity to form the system.
(c) Potential energy, U = Potential difference x Charge