No. Ren'py is just a core engine, and one mostly oriented to Visual Novel, it have nothing that regard the game mechanism.
You have to create your own variables for everything that regard the game mechanism, and in fact create your own game mechanism.
Er, not at all, Character is a class object (well, technically it's a function interface for a class object), not at all a string.
Some devs extend the class to add their own variables, and so group them together with the generic Ren'py object. But it's not recommended, because the said class isn't intended to be saved, and also evolve with time, which can lead to name conflict for the attributes.