Posts in these groups are read by Microsoft staff, and, on occasion,
responded to by them.
However, the norm is peer-to-peer support. This means that a response will
be from another user of the product. You will need some experience to judge
how to weigh that response, I'm afraid--there's no simple guideline I can
offer.
Messages and responses posted here are read by somewhere between hundreds
and thousands of others besides those involved in the original exchange, so
sometimes it is worth responding to something which really doesn't directly
seek a response.
You asked reasonable questions about the difference between a released
product and a beta. I gave what I think are some of the factual answers to
those questions.
The FAQ is, indeed, an unofficial set of responses, housed on a
non-Microsoft site. There is a FAQ about the beta at Microsoft's site,
located here:
http://www.microsoft.com/athome/security/spyware/software/faq.mspx