Heroic Favicon Generator is your one-click favicon generator for WordPress.
A. Be sure they are enabled on the settings page and clear all caches (on your sever and browser) and hard refresh the page.
A. Simply delete the favicon.ico from the root of your WordPress install or be sure to uncheck enabled for all favicons sizes before uninstalling the plugin.
A. No worries, simply ask on the support section on WordPress.org.