What is the ruling on the discharge that comes down after seeing dryness and before the white discharge, and is it considered part of menstruation or not, and what must a woman do in this situation?

What a woman sees of brownish discharge before seeing blood is, according to the preponderant opinion, not considered menstruation. As for the days she sees blood, all of them are menstruation. If she sees dryness, she has become pure. Seeing the white discharge is not a condition; purity is achieved by one of two signs: dryness (inserting a cotton swab and it comes out clean) or the white discharge. Whichever of these two signs is found first, purity has occurred, and ghusl (ritual bath) becomes obligatory.

As for what a woman sees after purity, such as yellowish or brownish discharge, it is not considered menstruation. Her performing ghusl after the cessation of blood and seeing dryness is a correct action, and her husband having intercourse with her in this state is permissible. If she sees blood after this within the possible time frame [of menstruation], there is no sin upon her for intercourse and no expiation; for the purity that interrupts menstruation is a valid purity. If she sees blood after her husband has intercourse with her, at a time when this blood could be menstrual blood, she must perform ghusl again.