Multisite setup on local development environment
Not sure what exactly you want to do.

Multi-site is usually used to create separate drupal installation from the same drupal folder. To create one, you need to copy default/default.settings.php to yoursite.com/settings.php, make it writable and then visit the site, which should present you with the installer.

You only need to something with sites.php if you want to override the default domain mapping and e.g. also server siteB.com from sites/siteA.com. Also, Drupal doesn't search for a settings.php in 'all' but 'default'.

Your naming scheme sounds more like you want a mobile version of your site, which usually just implies that a different theme is used and some other mobile specific things. There are modules which can automatically changing the theme when the site is requested by a mobile browser.