How to enable / disable to edit explicit single elements? (editable, isEditable, ... )

Heyho and hallo!

I'm frustrated and finally helpless. I've tried everything and searched and googled and so on, but I can't find a explaining Sample Code... So: Please help! :-)

I working on a plugin for CKEditor 4. Now I try to disable the editing in the whole editor, except one <h1>- and one <p>-Element. I have something like that:

[ ... ]
function( editor ) {
    editor.insertHtml( 
        $( '<div>' ).append(
            $( '<h1>', {
                 id: 'inputAllowed'
             } )
        ).html()
    );

    editor.wishMethod.makeAllNotEditable = true;
    editor.document.find( '#inputAllowed' ).getItem( 0 ).isEditable( true );
}
[ ... ]

I simply not get, how to manage this. How to get 'editable()' and 'isEditable()' to work.

I'm thankfull for every helpfull advice! :-)

Thanks a lot!

HenLen