4. You cannot reserve FastPass+ times in multiple parks on the same day without Park Hopper. If you do not have the Park Hopper option on your tickets, the system will preclude you from making FastPass+ selections at multiple Disney theme parks on the same day. If you do have the Park Hopper option on your tickets, you can make selections for FastPass+ times at more than one park per day, but you’ll still be limited to only three initial selections total per day.
10 Tips and Tricks for Using Walt Disney World’s FastPass+ System