optional (double pages, facing pages)

Hi I'm new to the forum and I was wondering if anyone has any experience in the new KF8 Feature?
Before I even try it on my own and see what it does.
The optional (double pages, facing pages) page 31 4.2.5

First question.
Is this all that needs to be done in the OPF to use this feature or do I have to add additional metadata to the html file as well.
<itemref id="page-id" properties="layout-blank"/>
<itemref id="page-id" properties="page-spread-left"/>
<itemref id="page-id" properties="page-spread-right"/>
<itemref id="page-id" properties="facing-page-left"/>
<itemref id="page-id" properties="facing-page-right"/>

If my understanding is correct.
I have a book that is a fixed layout at 1024x600 any mode. I not only can display the two page spread that is comprised of two images (512x600) but a can also have only one side of the two page spread, left or right, to be displayed in portrait mode?

If I'm on a Kindle Fire, how does one side of the two page spread image (512x600) fit into a view size in portrait at 600x1024? I mean it says it can change on the page level?

Can anyone explain this feature and how it would work on a Kindle Fire?

Thanks