The diagrams that I’ve seen of SFPF are on a flat building lot. Can SFPFs be used on a sloped lot? How sloped?

Can they be used for a walk-in basement, where only the “front” of the foundation is shallow?

Can they be used when the slab is just above the level of the ground at the high end of the foundation, so at the low end of the foundation two, three, or four feet of foundation may be exposed before being buried the recommended 12-16″ (zone 6A)? Is is sufficient to insulate the exposed concrete with 2″ XPS, or is a thicker layer needed, or is a second layer of 2″ foam needed on the inside of the concrete (other than the six inches that are used to insulate at the top of the foundation, between the foundation and slab)?