Barcelona (Spain) > Shenzhen > Hanoi (Vietnam)

One more question please, will the 24-hour visa free transit permit allow us to get out of the airport in Shenzhen and visit the city during our layover time there? We won't need to wait at the airport, right? I will really appreciate to receive your clarifying reply, thanks!

If Shenzhen is your only stop in mainland China, you will be covered by 24 hour visa free transit and you do not need any kind of visa. So, you will just transit through Shenzhen and here there is no any problem because nobody will ask you for a visa. The other thing is if you want to exit the airport and spend some time in the city or to have an overnight in the hotel outside the airport. In that case, the first upon landing will be to approach 24/144 hour visa free transit where you will apply for a temporary entry permit. This application is for free and you will present here your flight tickets as well as your accommodation booking confirmation in hard copy. After a short check and since your layover is long, I would say that your chances to be granted that permit are practically certain. Please, just do not confuse 24 hour visa free transit, because this is your right with temporary entry permit that comes as a bonus.