How Big Is Assassin’s Creed Origins? And Other FAQs Answered

Is there multiplayer in ACO? What are the microtransactions like? How does Origins compare to other Assassin’s Creed games? Is Senu (the bird) necessary to use? Are any parts of the map restricted by level or story progression? What are the difficulty settings like? These questions and more are answered as I auto-pilot-horse across the map.