Is my ghusl and prayer before the cessation of blood, provided the menstrual period does not exceed 15 days, valid, and must I wait until complete purity in every cycle, and must I make up the days I fasted?

The maximum duration for menstruation is fifteen days. If the blood exceeds this period, the woman becomes a mustahadah (experiencing prolonged vaginal bleeding). In this case, she should refer to her previous habit. If she does not have a habit, she should act according to reliable differentiation (between menstrual and non-menstrual blood). If she cannot differentiate, she should consider six or seven days of the month as menstruation.

If the ruling of istihada (prolonged bleeding) is established, you should perform ghusl (ritual bath) after the expiry of your customary period and do not wait to see purity. However, if the ruling of istihada ceases, meaning you observe purity for fifteen days, then you should wait until you see purity along with the returning blood.

You are not required to make up the days you fasted during istihada, because the fast of a mustahadah is valid. However, if your fasting occurred during menstruation, then you must make it up.