Is it permissible for a woman to suffice with wiping the front part of her head in Wudu'? And what is the ruling on her Wudu' and prayers if she has done that for most of her life? And what is the ruling on wiping over a bun or neglecting a small part of the sides of the head?

Wiping the head is one of the pillars of ablution. A woman limiting herself to wiping only the front part of her head contradicts the view of the majority of scholars, and it is a weak opinion. However, she is not required to repeat past prayers. As for a hair bun (ka‘ka), it should be wiped over during ablution, and it is not necessary for the water to reach the scalp. If she did not wipe over the hair bun or a small portion remained unwiped, her ablution is still valid according to some scholars. Nevertheless, she should wipe her entire head in the future to avoid scholarly disagreement.