Visit to Great Wall when on 72hour visa free transit in Beijing

Hi , My daughter and I fly from Osaka Friday July 31 with a flight change in Shanghai arriving there Friday 20:40 and go fly again at Saturday at 7 am to Beijing (we will not lieve SH airport.) arriving in BJ at 9 am. We have a flight to Copenhagen on Monday 13:10. Are we permited to 72 hours free stay in China then? And are we allowed to take the train from BJ to Badaling to visit the Great Wall during our stay in BJ
Niels from Denmark