Are you talking about multiple sites in multiple tabs or just opening several tabs from the same site? It should count your separate tabs as one visit opening all those pages.

It depends on the status of the old domain. A few questions I would have are

• What was on the original domain?
• Is what I'm going to do with it related to that?
• Will any backlinks to that domain link still want to link to my new site?
• Was the original site still indexed with the various search engines or was it involved in questionable activity that got it devalued?

The simple answer is no. Let's say you have page A and 301 it to page B. As soon as Googlebot gets the 301 (might take a bit longer but for argument's sake we'll say it's instant) it drops page A and indexes page B. As the ranking process moves along (which is slower than indexation) most, if not all, of the PR that A had is now moved to B.

Google can't read your htaccess file (Apache will not show any page with a period as the first character in the filename for security reasons) and I've not heard of any long term penalties from changing URLs. Just realize that there is a gap (days or weeks) between the time that Google notes A moved and B is ranked like A was.

I'd go with phpBB. It's Open Source and has several popular mods, including some for SEO.

Some paid software is also SEO friendly, including software like vBulletin and xenForo.

If you really want to go this route, add this to your site .htaccess

RewriteCond %{SCRIPT_FILENAME} !-d
RewriteRule ^([^.]+)$ $1.html [NC,L]

So domain.com/file will access file.html

Again, the caveat is there is a short term SEO hit for doing this. Long term, you should be fine.

I would pick #2, where you process .html files with PHP. Changing URLs involves taking a temporary SEO hit and I would not recommend doing it.