To answer your first question: the answer seems to be yes although their docs don't make it entirely clear.
Their docs say:
Here is an example of how to instantiate the client, and retrieve the Root List Resource resource:
Before the code snippet your pasted. That makes me think that the url being passed is whatever you're trying to use, e.g., you could have that set up on a networked machine called monty_python running on port 5050, then you would do:
client = RBClient('http://monty_python:5050/')
As for a test server you should check the documentation they have about their Web API.
Their examples don't seem to show any authentication being performed in the overview. If you check in other sections (e.g., Tutorial: Creating a Pull Request) you'll see them demonstrate how to authenticate and what can be done after authenticating.
As for your last question, I'm not 100% sure what you're asking, but you should probably check the docs I found for their Web API