Does a menstruating woman have to change her clothes once her period ends?

She gets brownish spotting before the bleeding starts

Her menses ended but there is still some blood in the urine; should she fast?

Does she have to insert a piece of cotton to check whether her menses has ended, or is it sufficient to wait for twenty-four hours and then do ghusl?

Her period became irregular as a result of taking the pill; what should she do?

Can Women Cut Nails during Menses in Islam?

Brownish discharge one day after menses ended

If a woman makes a mistake about when she becomes pure following menstruation, is she sinning?

If she had an IUD inserted, then her period got longer, then she suffered prolonged non-menstrual bleeding, should she follow her cycle before the IUD or after it?

She had some secretions in which there was a thread of blood