This plugin provides alert message for duplicate post title and unique post title when adding new post.
Install and activate plugin, then create new post with title that is already exists, once you enter title and press tab or move to another field it will show highlighted message for duplication.
Yes you can customize or expand plugin to also check uniqueness of title for custom post types and pages with minor changes.
Yes, this plugin only provide message that this title is duplicate but same time it also allow to save the post with duplicate title and it will work as default wordpress functionality.
Yes, this plugin provide unique title message.
No, but if you need any suggestions how to customize this plugin then you can let us know here http://www.webconfines.com/contact-us
It is only available for posts