Is prayer and fasting obligatory for the physically and hearing impaired person who is aware and understands, or is expiation (fidyah) for fasting obligatory upon his guardians?

The sick person is required to pray to the extent of their ability. If they cannot stand, then while sitting. If they cannot sit, then on their side, and they should gesture for bowing (ruku') and prostration (sujud), making their prostration lower than their bowing. If they are unable to do that, they should gesture with their eyes and intend with their heart. Prayer does not cease as long as the mind is sound. Similarly, fasting is not waived for them as long as they are sane, capable, and do not have a valid excuse for not fasting.