Is an elderly person who does not fast required to feed one poor person or several poor people each day, taking into consideration that the recitation of Hafs is "feeding a poor person" (إطعام مسكين) and the recitation of Warsh is "feeding poor people" (إطعام مساكين)?

The differences between the Quranic recitations are differences of variety and variation, not contradiction and opposition. All of them are truth that must be believed in and acted upon according to their contents. They are akin to one verse with another, and their multiplicity expands the meanings. As for His Almighty's saying: "And upon those who can afford it is the ransom of feeding a poor person," some recited it in the singular form "poor person," meaning feeding one poor person for each day of breaking the fast. Others recited it in the plural form "poor people," meaning feeding poor people for the entire month, or that each one of those who break their fast feeds a poor person, thereby achieving the feeding of a group of poor people. There is no contradiction between the two recitations, as both are valid.