What is the correct way to perform ghusl (ritual purification) after menstruation? If I’ve been doing it incorrectly, are my prayers and fasting over the past years invalid? And what is the proper method for ghusl after menstruation and major ritual impurity (janabah)?

There are two types of ghusl (ritual bath): the sufficient and the complete. The sufficient involves dousing the entire body with water, along with rinsing the mouth (madmadah) and nose (istinshaq). The complete is that which the Prophet, peace and blessings be upon him, performed in the well-known order. There is no difference between the ghusl for janabah (major ritual impurity) and for menstruation, except that for menstruation, it is recommended to rub the hair vigorously and apply perfume to the area of blood. Uttering "Bismillah" (in the name of Allah) before ghusl and wudu (ablution) is recommended, and obligatory according to the Hanbalis. Rinsing the mouth and nose are obligatory in ghusl and a condition for the validity of purification according to the Hanafis and Hanbalis. For one who did not perform them in the past due to ignorance, their ghusl and prayers are valid, and they are not required to repeat them.