What is the ruling on the brownish discharge that appears at irregular intervals, either preceding the menstrual period or coming in its place, and what should a girl do regarding prayer in this situation?

Brownish discharge (kudrah) is not considered menstruation unless it occurs during the accustomed period or is connected to blood. If a woman does not have an accustomed period, it is not considered menstruation unless it is connected to blood; otherwise, it is irregular bleeding (istihada). As for blood, whenever it is seen at a time when it is possible for it to be menstruation, it is considered menstruation.