most (not all, some contributions are QTVR-only due to historical reasons)
many, but depends on photographer's choice of file upload (newer event = more likely to work) and your device's capabilities. You may experience slow playback, distorted images or unexpected browser quitting if there is only limited memory/GPU power available.
Beijing, the Capital of China, has a population of 13,000,000 and transient population of 3,570,000
The total number of vehicles have been over 2,700,000. In order to guarantee the priority in public transportation, many bus-stops were reconstructed like this one in Demaozhuang, south-east of Beijing.