Short answers, pulled from the story.
Apartment is the standard term in North America, while flat is the common word in the UK, India, South Africa, and traditionally in Australia. In the UK, property developers have more recently adopted apartment to describe expensive upmarket flats, particularly in exclusive areas such as Belgravia and Hampstead in London.
The Puebloan peoples of the American Southwest built multi-room dwellings of more than 900 rooms from the 10th century onward. The ancient Roman insulae reached ten or more stories in imperial cities, and medieval Fustat in Egypt housed residential buildings of up to fourteen stories, described by Nasir Khusraw in the 11th century as having roof gardens irrigated by ox-drawn water wheels.
A Russian communal apartment, known as a kommunalka, is typically a cluster of around five room-apartments on a floor of a pre-Revolutionary mansion, sharing a common kitchen and bathroom. Traditionally a room was owned by the government and assigned to a family on a semi-permanent basis.
Albert Mansions on Victoria Street was constructed between 1867 and 1870, making it one of the earliest blocks of flats in England. Philip Flower built it and James Knowles designed it; its tenants included Sir Arthur Sullivan and Lord Alfred Tennyson.
In a cooperative apartment, tenants do not own their individual units but instead own a proportional number of shares in the corporation that holds the entire building. In a condominium, residents own their individual apartments outright and pay a monthly or yearly fee for building upkeep. Co-ops are common in cities such as New York.
Loft apartments developed in the mid-20th century from former industrial buildings, typically 19th-century warehouses and factories left vacant after changes in town planning rules and economic conditions. Artists and musicians seeking large spaces in cities such as New York were drawn to them, and some early occupants lived in these buildings illegally as squatters.