1 - Does =?cc regenerate (rename) the combined .css and .js file?
… or does something else?
2- With the .htaccess setting expiry for .js and .css 1 year out… what happens with those .js and .css files from add-ons that ARE NOT part of the combines .js and .css? my guess is they stay cached by the browser(causing us problems).
Any help with be appreciated.
Yes, 'cc' clears the 'static' files which includes css and js files.
Note that 'ctpl' clears the template cache so generally if you're going to do '?cc' you might as well do '?cc&ctpl'.
The expiry of the caching simply indicates the “maximum” time the file can be cached in the browser without updating. If the file on the server is newer than the one in the browser cache then the browser cache is always updated.
If a year has gone by without the file being updated in the browser, then the next access will cause it to be reloaded from the site.