Entry into china re visas whilst cruising

Am I right in assuming that if I am on a cruise ship into Shanghai and book at tour there then I would be eligible for the 15 day free visa for cruise tour groups and would be able to enter Beijing (Tianjin) 4 days later on the same ship without needed any additional paperwork ?
Also does the tour have to be booked via an independent Chinese tour operator or can it be booked using the Princess Tours ?