What is the ruling on praying for one who suffers from an irregular menstrual cycle, and whose menstrual bleeding continued for more than three weeks? And must one make up the prayers missed in this situation?

The basic principle is that the blood descending from a woman is menstrual blood unless it continues for a full month, or stops only for one or two days, in which case she is considered to have irregular bleeding (istihada). There is no maximum limit for menstruation; it can increase, decrease, come early, be delayed, or even stop. A menstruating woman does not pray or fast. However, a woman with irregular bleeding fasts, prays, and her husband may have intercourse with her. What is descending now is menstruation, unless it continues for a full month or stops one or two days before that, in which case it would be irregular bleeding.