2 Facebook does not allow you to change the "What's on your mind?" text box, unless of course you're developing an application for use on Facebook.
Learn how to create a Facebook share link without using JavaScript, including tips and solutions for effective sharing.
In the facebook developers console for your app, go to App Review-> Permissions and Features. Set the public_profile and email to have advanced access. This will allow all facebook users to have access and these two settings are auto granted. Ensure the Access Level indicates Advanced Access
How to resolve Facebook Login is currently unavailable for this app ...
For my application I need to embed Facebook page in an iframe, here is the html code: