From Facebook Developer Wiki

With Facebook Connect, you can make calls to the Facebook Platform REST server -- http://api.facebook.com/restserver.php.

By and large, the API is fully supported, with some exceptions. Facebook Connect provides additional JavaScript methods (like stream.* methods) as well as XFBML (which is an extension to FBML, the Facebook markup language). You can't make any API calls that require your application secret, such as admin.getAppProperties, admin.setAppProperties, fbml.setRefHandle, and the Permissions API.

Moreover, you'll need to use the JavaScript library to perform the following actions that require AJAX dialogs when called by the REST API:

• To log in a user, you should use requireSession. You can't use the requirelogin attribute.

• To use Feed forms, you should use the FB.Connect.showFeedDialog.

• To prompt for extended permissions, you need to call showPermissionDialog. You can't use the promptpermission attribute.