Is it obligatory for a woman to perform ghusl and pray if her menstruation comes ten days after her previous period, knowing that she saw a light yellowish discharge between the two periods? And is it true that the minimum period of purity is fifteen days?

There is no minimum limit for the period of purity between two menstrual cycles. Rather, whenever a woman sees the black, malodorous, well-known menstrual blood, she must cease fasting and praying, provided that the total duration of menstruation does not exceed half a month (fifteen days). As for yellowish or brownish discharge after purity, it is not considered menstruation and does not share its rulings.