ANSWER:

What is mandatory is to wipe it once. Going back to the front is sunnah.

You can also wipe it from the middle of the head downwards and that would be sufficient.

While doing wudu, it is obligatory to wipe over your head from its front to its back. But Is it obligatory or sunnah to wipe your head from back to its front. Our wudu is valid if we skip it? Because when women with long hair do, it’s difficult.