question about routes and filter

For your second question, yes you should be able to set a route for get and post. Something like this:

PHP Code:

$routes->group('admin', function ($routes) {
    $routes->add('foo', 'Admin\Foo::index'); // any verb (GET, POST, PUT, DELETE…)
    $routes->get('bar', 'Admin\Bar::index'); // GET only
    $routes->post('biz', 'Admin\Biz::index'); // POST only
    $routes->match(['get', 'post'], 'baz', 'Admin\Baz::index'); // GET or POST only
}); 


See :
Grouping: http://codeigniter.com/user_guide/incomi...ing-routes
HTTP verbs: http://codeigniter.com/user_guide/incomi...-in-routes