I can't answer your request filter question, but based on what you've said you're trying to do, there are other options.

Create additional portals for VersionB and VersionC (they can be Child Portals).  Change the settings of the home pages for those portals so that the Link URL points to the specific page in VersionA that you want.

Bump!  I'd still like someone to weigh in on my original questions abount using the Request Filter to redirect domains to pages.

Thanks in advance to anyone who can tell me if this will work and how it should be setup. 

For anyone interested, my example in the forth post in this thread actually worked.  Problem solved and it works like a champ.