Arriving Tianjin for 3 day fully escorted tour Beijing then fly to Frankfurt, 72 hr free transit ok

We disembark our cruise ship, Ovation of the Seas at Tianjin 26/4 for a three day tour in Beijing departing on 29/4 Lufthansa flight to Frankfurt.
My questions are;
Are we entitled to use the 72 hour free option?
Can we obtain appropriate visa stamp at Tianjin port of entry?
How do we ensure cruise ship staff will allow us to board as they appear to require proof of visa at embarkation point?
Been struggling to get clear answers elsewhere, thanks for any help.