Is blood that appears on the fifth day after the usual menstrual period ends on the third day considered istihada (non-menstrual vaginal bleeding), and are prayer and fasting permissible with it?

This drop of recurring blood is considered menses, and ghusl is obligatory after its cessation. If ghusl has not been performed, it must be done immediately, and the fast of the day on which the blood was seen must be made up. As for the fasts of the subsequent days, they are valid. The prayers performed after the blood recurred and ceased must be re-performed, according to the majority of scholars.