Weew,
I am not at all an expert on roses. Just started growing some myself! But I think I can answer a couple of your questions:

#5. I'm pretty sure all roses can be eaten. But if you are growing them to eat, you will have to be careful not to put any toxic chemicals on them. Then they would be dangerous to eat.
#4. I think roses will form the hip in your area, but as I understand it, not all rose varieties form hips. So if you want to get rose hips, too, you will need to make sure that you're growing a kind of rose that makes hips.
#3. This one I'm not 100% sure of, but if it were me, I'd buy a container slightly larger than the size of the root ball of your rose. As the rose grows, you'll need to keep checking to make sure the roots aren't getting pot-bound. Then you'll have to re-pot it into a slightly larger container. (As I said, this is not an expert opinion, just my guess. Maybe someone else can help.)
Carolinakate

Thanks Carolinakate. But I still need to know about the petal?

The petal is okay to eat. When I researched the internet, the sites I found said not enough research had been done on the nutrient content of rose petals to know what they contain. Most research focuses on the rose hips which are high in vitamin C.

Here is a link that might be useful: Rose petals