SPRINGFIELD — Four cases highlighting the Illinois Supreme Court’s September term aim to answer the same, big questions: Who’s liable, and to what extent?The rub is that the state’s top justices, who are back in session for oral arguments today, will tackle them in two vastly different settings: hospitals and bike trails.The high tribunal will consider whether a nearly 25-year-old precedent allows a hospital to be held vicariously liable for negligent care at a separate clinic. They’ll also …