The subject is cut out by a neural net; the background is yours. No prompts.
Background replacement without generation is the most predictable option: you know exactly what ends up behind the subject. Ideal for catalogs, avatars and collages.
Yes: a second file becomes the backdrop — scaled to cover the frame.
Sure — pick one with the color picker.
No. The cutout is neural, but the background isn't invented — it's your color or image. That's why it's free.