Is it obligatory to perform ghusl again and make up the prayers if menstrual bleeding stopped, then returned after performing ghusl on the sixth day of irregular menstruation?

The blood that has recurred is considered menses, as it falls within a period suitable for menstruation. You must perform ghusl again after it ceases. The prayers you performed during the intervening period of purity are valid and do not need to be made up. However, if you omitted prayers during those hours, it is more cautious to make them up. The purity that intervenes within menstruation is a valid purity, and a woman during this time has all the rulings applicable to those who are pure.