On "System Domains" and compiling

programming flash
1

I’m going through Sencular’s article on Application Domains and had a few questions on it.
http://www.senocular.com/flash/tutorials/contentdomains/?page=2

Just as a quick check, the classes in the “System Domain” is included by the currently running Flash Player, NOT included at compile time, correct?
This would mean two things:

  1. The bytecode for the classes won’t add to the file size of your SWF.
  2. If these classes change or are updated in future versions of the Flash player, a SWF compiled for an earlier version will use the most up to date version of the class in the Security Domain, not the one it was compiled with.

Am I correct so far?

If that is true, are ALL classes in the “flash.*” package part of the System Domain (meaning, none of those are considered “defined” in the compiled SWF) or are some of the classes written in AS3 and included with the SWF at compile time?