What is the ruling on a patient with Alzheimer's, who has lost their memory and comprehension, abandoning prayer and fasting?

If an Alzheimer's patient's dementia worsens to the point of losing their mind, they are no longer held accountable (mukallaf), so neither prayer nor fasting becomes obligatory upon them. However, if they still comprehend matters and are aware of their actions, they should perform prayers in the manner they are able. If they are unable to fast, they may break their fast and feed a poor person for each day missed.