When a writer wants to make a story seem authentic, which of the following might the author include?
descriptions of activities or events
several recommended reading lists
footnotes at the bottom of each page
author notes detailing research done

The appropriate response is the first. You don't make a fiction story appear to be bona fide by including commentaries or references yet you do this when the subject is genuine like history. None of this is about fiction - where you make it up as you compose. At that point, you require activity or occasions to make the book appear to be practical. At the end of the day, a book set in 1944 in England better specify the Second World War or a book set in Germany in 1977 ought to say East and West Germany as independent countries.