All the doors are categorized based on their Nominal Size. There are two ways to find your size. Search by slab size.  Search by unit Size.  Search by slab size.  Go to any catalog page on the website and filter the closet nominal size of the slab and sidelite that you would need to build your unit.  Then filter the door configuration on the left navigation  Then go to the product page to customize even more.

Yes, you can.  Find the door you like on the website in the "single door" configuration. Open click on the customize button and choose "slab" under Door System Kit or Prehung Option.