What is the ruling regarding prayers performed without purity for years due to a mistaken understanding of the end of menstruation, and must the questioner make up past fasts that she did not count?

A woman becomes pure from menstruation by seeing the white discharge or by the complete dryness of the area. The questioner's ghusl (ritual bath) before the end of menstruation is invalid, and consequently, her prayers and fasting during that period are null and void.

Scholars differed regarding the obligation of making up for acts of worship for one who was ignorant. Some held that there is no obligation to make them up, based on the hadith of the man who prayed poorly and the woman with chronic vaginal bleeding (mustahada). This is the choice of Shaykh al-Islam Ibn Taymiyyah. However, the majority of scholars are of the opinion that making them up is obligatory, and this is the more cautious approach.

Therefore, it is obligatory to make up the prayers and fasting that were missed and occurred during menstruation.