most (not all, some contributions are QTVR-only due to historical reasons)
Javascript + HTML5 / WebGL
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.
In the 1960's homes were built with fences as borders between homes. We have a dog so this act as a great border between properties.