Display a page inside another one

Hi,
I’ve googled a lot and I’ve tried a lot of possible solutions (ex. subpages, plugins, etc) without finding the right way to solve my problem.

In my theme (https://www.laurarabbione.it) I have a frontpage with 4 columns.
I need to display a random page at the bottom of the 4 cols group (one page per time).
The “random page” must be previously selected by the administrator (or the site owner) in a range of pages excluding other pages (ex. I need to display at the bottom of the page F the pages A, B, D – one per time – and not C or E).

I need to display the page and not only the link.

How can I do?

Thanks in advance.