Why would you want to download an outdated version of the demo when you can download the current version of the demo, which is better?
You don't want to play them. There's no reason to. They are exactly the same, just fewer features. They don't look any different, they don't play any different.
Disable the v15 bricks and turn of upnp and you're at v9.
Disable the terrain blocks, v15 blocks, upnp, and chat censor, then don't place any events and you're at v8.