In a web site like this one, built with Responsive Design, what you see on the screen is dependent on the size and aspect ratio of the screen itself. Every device on the internet now reports its screen size to the web server. The server then determines how to format the screen and display the data, based on that information.
The smaller screen size of the iPhone 4 did not allow room to display the Recent Posts column. The larger screen if the iPhone6+ has room for it, so it gets displayed. That's how Responsive Design works.
