The following demo shows how to use simple JavaScript to retrieve all Feedback items in this app. It will also offer a delete-button to delete again.
This uses jQuery to do the ajax and will add the returned items to the ol-tags.
Note that it works for admins by default. The permissions have not been opened, so it wouldn't work for non-admins. To make it work for visitors you have to allow read-permissions (to get the list) and delete permissions (to delete) for anonymous users (or users with view permissions). This is configured on the content-types - for more infos read Permissions Help.