The list of runbots cas be accessed from https://runbot.odoo.com/ or by downloading the addon listed on the presentation page.

All these rectangles are different instances of Odoo databases, sorted by version. You can access any of them and play with them, just choose your version of odoo and which instance you want to access (community, enterprise or design-themese)

No, there is no need to configure or install anything, everything is preinstalled and preconfigured. You can directly access the db by pressing on the 'enter' logo next to one of the odoo solutions (odoo, enterprise, design-themes).

Well, you can just leave the database and it will rebuild itself at some point in the day.