No you can't go back to the walled town unless there is some key out there that can open it but otherwise nope but if you travel to other realms you can go back to them through the portals.

No, but you can go back from each realm to another.

O well thanks for the quick answer.
In the walled city. Who runs across the entrance of the Park with the fountain where you start?

i believe that was ermac. don't think there's anything you can do with him though

That's what I thought. Red and Black out fit.