Is it necessary to wait until the yellow discharge completely disappears, or is it sufficient to perform ghusl immediately upon seeing dryness, and what about making up the missed prayers due to doubt about purity?

If a woman sees the sign of purity (ṭuhr) by dryness, she must hasten to perform ghusl (definition) (ritual bath) and prayer. Yellowish or brownish discharges after purity are not considered menstruation. If she delays prayer past the time of purity, she must make up for the missed prayers. If she doubts the time of purity, the default is that it has not occurred, and she should attribute it to the closest probable time.