Is it obligatory to pray after the fifteenth day of menstruation if bleeding continues and has the characteristics of menstrual blood, and must the prayers of that period be made up?

If the blood flow exceeds fifteen days, the woman is in a state of istihadah (non-menstrual bleeding). She must refer to her previous custom if she knows it. Otherwise, she should use valid discrimination (between menstrual and non-menstrual blood). If neither applies, she should consider six or seven days of the month as menstruation and the rest as istihadah. She must make up the prayers for the days she missed, thinking she was menstruating, as this is the more cautious approach.