What is the ruling on prayer if menstruation ceases for three months then returns with a flow greater than the usual number of days? Should the usual number of days be counted, followed by ghusl and prayer, or should one wait until all the blood has descended before performing ghusl?

The maximum period of purity between two menstrual cycles has no limit, and the three months mentioned are all a valid period of purity. The maximum duration of menstruation is fifteen days. If the bleeding stops before this period, all of it is considered menstruation. If it exceeds it, the woman is considered to have Istihada (non-menstrual vaginal bleeding).