Is a patient with frequent flatulence due to irritable bowel syndrome excused from his ablution and prayer? And should he complete his ablution if gas is released during it?

The emission of gas is either continuous, where you do not find enough time to perform purification and prayer without it ceasing, in which case your ruling is that of a person with incontinence. You perform ablution after the time for prayer begins and pray as much as you wish with that ablution, and what exits from you does not harm you. Or, its emission stops at a known time, sufficient for purification and prayer. In this case, you must wait for this time to perform ablution and pray therein with valid purification, even if you miss the congregational prayer.