Agree on B. You can also achieve currency by flying one hour IF with an instructor. (I guess this could be construed as ICUS), including an approach.
Not too sure about this. Whether the person is an instructor or not doesn't really matter - if it's dual they do need to be an instructor, but dual won't cover you for your single-pilot currency - and you don't need to be an instructor to supervise ICUS.
If there's any instruction given (instructor rating or not) then the flight can't be logged as ICUS in the first place.