Is it obligatory to make up the Asr and Maghrib prayers if a yellowish discharge appeared before menstruation, and then menstrual blood followed? And is it obligatory to repeat the Isha prayer if a woman purified herself from menstruation with a small amount of light blood, but did not perform ghusl until several hours later?

The yellowish discharge before menstruation is not menses, and the prayers performed by the questioner before seeing clear blood are valid, provided she performed ablution after the discharge. However, after seeing blood, her purity cannot be confirmed except by seeing dryness. If she sees purity after the time for Fajr prayer has exited, she is not required to make up the ‘Isha and Fajr prayers.