What are the signs of purity from menstruation, and are the abundant white discharges that appear after the yellowish discharge considered "al-qassah al-bayda'" (the white discharge), and is it obligatory to refrain from prayer and fasting throughout this period, and is tracking the trace of blood with a cotton swab specific to married women and not to virgins?

If discharge appears after menstruation has ceased, indicated by dryness, then it is of no consequence and is not considered menstruation, even if it is yellowish. This is based on the statement of Umm Atiyyah, may Allah be pleased with her: "We used not to consider the yellowish or brownish discharge after purity to be anything." There is no difference between a married woman and others in the method of confirming the cessation of menstruation.