1. Both ClassiPress and Vantage are stand alone themes, so they require their own instance of WordPress to run. If you're looking to add functionality to either of the themes, then this would ultimately require customization on your part. You could, however, potentially use both themes on a single website without the need for major customization, and an example of how this could be done would be to install the themes in a separate subdirectory
e.g.
yourdomain.com <== Your Vantage installation
yourdomain.com/classifieds <== Your ClassiPress installation
2. Neither theme has a feature built in which detects the location of the site visitor, so again this would require customization of the default theme code in order to add the functionality you describe.
3. This really depends on whether or not you plan to make some major changes to the default theme (either ClassiPress or Vantage), or choose to use both together in a manner described in #1. If you were looking to use more than 1 theme on your site, then you may want to look at a
multisite setup which would allow a single login across all installations.
I hope this information helps. Thanks.
