I expect my mother to only use 2 days of a 4 day hopper pass --- Will I be able to use the remaining 2 days on a different trip for myself or someone else??
Absolutely. Just not on the same day at the same time. We just gave our daughters the last day of our US/IOA tickets to use during their trip. The only thing a person should NEVER do is buy unused day tickets from a stranger or on-line.