Not exactly. All facebook employees run the latest build, and it gets tested that way before it gets pushed to live.
Yes, exactly. Facebook only has one branch, trunk and it's SVN. Developers version on their own machines with Mercurial, git or whatever then commit directly to trunk. That gets pushed out to staging then production with Chef.
This is vastly different than the continuous integration cycles at other companies of comparable size in the IT services business.
Facebook is still able to change rapidly because it never gave up the model from when Mark Zuckerberg started it. Microsoft gave up the 1975 Albuquerque model in the mid 1980s. One day Facebook will slow down significantly and get old too, and it probably won't be too far in the distant future. It's already starting. That IPO BS put a huge dent in the bumper.