Is the Ghusl considered valid if one forgot to pour water over the entire body, and must the prayers performed with this Ghusl be made up?

Ghusl is only valid by pouring water over the entire outer body. Intention and pouring water over the entire body (hair and skin) are obligatory without dispute. Therefore, whoever misses a part that water did not reach, then prays with that ghusl, must complete the ghusl and repeat the prayer. There is no sin upon him for forgetting.