How can menstruation be distinguished from istihada (non-menstrual vaginal bleeding) in a case where the menstrual period is irregular, ranging between 13 and 17 days, with no pain experienced, and what should be done regarding prayer and fasting in this situation, and what is the ruling in the Maliki school of thought?

The madhhab of the majority of scholars, including the Malikis, is that the maximum duration of menstruation (hayd) is fifteen days. The correct view is to consider 15 days as hayd and anything beyond that as purity (tuhr) if the bleeding continues without distinct characteristics (i.e., no differentiation between strong and weak blood).