Those hills are MUCH steeper than they appear in the photos. I often jog with Amanda so she can experience a little speed. She is really good about pedaling while I'm pulling her uphills so it's not like hauling dead-weight. Except when she thinks she's funny and stands on the brakes.
The leash is probably a 15 ft retractable. It is looped and clipped around the seat post of her bike. Amanda lifts up her foot when I switch to helping her up the hills. It's great that it's retractable so that as she speeds up or slows down the leash doesn't get tangled in her tires but I think a 10 ft retractable would be better so she stays closer to the stroller. (I have to thank one of my neighbors for the idea. It's brilliant.)