1. I wasn't allowed -- or able, either, I guess, cuz they took my crutches away. You're considered a falling hazard post-op and they want to keep you safe, so.... bedpan. Love it or leave it. Once I got all disconnected from everything, getting around wasn't any harder than after any other surgery that puts you on crutches, but I'd bet the hospital is gonna control you pretty strictly while they can.
2. Depends on a lot of factors, but odds are you won't LIKE the stairs at all. I'm five weeks post-op and still on limited weight-bearing with two crutches, so if that gives you any perspective, awesome. Some doctors have different post-op protocols which might have you going up and down stairs either way sooner than me or way later, your best bet is to ask.
3. My only previous knee surgery was a meniscus repair/lateral release. When I had that, I got myself ready with about two weeks' worth of frozen food, potato chips, soda in cans, etc. And I learned from that experience. Before the Fulkerson, I went out and bought FOUR weeks of food, snacks, and soda.... if I ever need another surgery I'll probably get even more. There's no such thing as making your home too convenient. Put in whatever work you can manage, bribe some friends or family or whatever, do anything you can to make getting around, getting the things you need, eating, icing, etc. as easy as possible. Other than that and some unavoidable and probably totally expected agony, you should be fine.