2 In cases like this the Wordpress adds a hash (unique id) to the function name and stores it in the global $wp_filter variable. So if you use remove_filter function nothing will happen

remove action from global $wp_filter

function my_remove_filter($tag, $function_name, $priority = 10){

    global $wp_filter;

    if( isset($wp_filter[$tag]->callbacks[$priority]) and !empty($wp_filter[$tag]->callbacks[$priority]) ){

        $wp_filter[$tag]->callbacks[$priority] = array_filter($wp_filter[$tag]->callbacks[$priority], function($v, $k) use ($function_name){

            return ( stripos($k, $function_name) === false );

        }, ARRAY_FILTER_USE_BOTH );
    }
}
my_remove_filter('plugins_loaded', 'my_action');