Leaving pudong airport on 24 hour visa free transit

Actually, whether you will be allowed entry permit or not depends on several details... First of all it is the length of your layover. In case that your layover is less than 8 hours, it is almost impossible to obtain entry permit. Also, in case that your layover is entirely during the daylight, it will be also hard to get the permit. In reality, the best circumstance is when your layover is longer one, especially when you have a good part of night. Please, keep in mind that the hotel booking in advance and having a confirmation in hard copy, will increase your chances. Anyway, in case that you have to change the terminals or in case that you fly on separate tickets and have to make new check-in, then an entry permit is just a logical consequence.

for the 24 hour transit to a third country, its up to immigration discretion if you can leave the airport or need to stay in the international transit area. If you are overnight with a hotel reservation that gives the best chance to visit the city.