What is the ruling on the prayers of a person during the past period in which he believed himself to be afflicted with سلس (urinary incontinence), and does he still have the excuse of سلس given the current symptoms, and how can he confirm the cessation of his excuse of سلس?

The body and clothes must be purified and ablution performed when certain of the exit of something from the anus, unless what exited is a small trace of istijmar, in which case it is excused. If the discharge stops for a period sufficient for purification and prayer, then the person is not considered to have salasil (incontinence), and is obliged to wait for it to stop, then purify himself and pray. There is no obligation to repeat prayers previously performed with impurity due to ignorance and presumption, because ignorance waives the repetition.