In chrome: Ctrl + F5 will flush the cache.
Version of set, as already said above, to get the browser to load the new version of css.
The version it is possible not to pay attention to is the same thing just delete the version, the effect is the same. The version is specified in functions.php presumably in a line of the form:
wp_enqueue_style( 'main-style', get_stylesheet_uri(), array(), '22.214.171.1243430030', true );
delete the last 3 parameters to:
wp_enqueue_style( 'main-style', get_stylesheet_uri());