Is ghusl from menstruation/janabah valid if the private parts are washed during wudu for ghusl? And if it is not valid, is it obligatory to repeat the prayers and fasting? And is it obligatory to deliver water to the inside of the navel or its outer part?

This ghusl is sufficient and complete. Touching the outer part of the private organ does not invalidate wudu. Even if something that invalidates wudu occurs during ghusl, it does not affect the validity of the ghusl. Water must be conveyed to the inside of the navel, without the obligation of removing any dirt within it, especially if its removal causes difficulty.