Can my family switch their O single entry visa to a multiple entry visa or extend it while it's still valid?

A user inquires about their family's O single entry visa, whether it can be switched to a multiple entry visa, or if they can extend it while it is still valid. The response clarifies that switching to a multiple entry visa is not possible and informs that a year extension can be applied for when there are 30 days or less remaining on the entry stamp. It also mentions that once the extension is granted, re-entry permits can be purchased.