You can get off the train on the platform to stroll around and buy the products on offer, but you have to continue on the same train. If you have bought a ticket on your own for only one of the intermediate stations, you must ensure that you can still buy a connecting ticket. It is advisable to go to the ticket office at the station and reserve a new seat. If you stay overnight at an intermediate station for more than 72 hours (3 days), you must register at a hotel or with the police in Russia.
Russian visas are valid throughout the country. If for some reason you miss the train by accident, the only options are to try to catch the train with a taxi and get on again at the next station. This is especially true if all your travel documents and belongings are left on the train. Once the train has stopped, there is no reason to go beyond the platform.
At the Mongolian/Chinese and Russian/Chinese borders, new bogies and axle pairs are replaced on each wagon. The changeover period is spent in the wagon and the changeover of the axles is monitored. The wagon is lifted slightly into the air and new “axle pairs” are put underneath. The changeover is due to the different track gauges in the countries.