Japandi, Scandinavian, mid-century, industrial, coastal, minimalist and more, or describe your own, like "warm modern with a green velvet sofa". You can also use an inspiration photo as the style reference.

Yes. The walls, windows, doors and camera angle stay as they are in your photo; the sofa, rug, lighting, colors and decor change.

Yes, but Virtual Staging is made for that: it adds furniture to an empty room without changing the floor or walls.