In what ways might living on a flat world be different from living on earth?

Please Google this. Here's one explanation:

Here's What Would Happen If The Earth Were Flat And You Ran All The Way To The Edge | HuffPost (http://www.huffingtonpost.com/2014/12/06/earth-flat-video-simulation_n_6275336.html)

Terry Pratchett wrote a highly-acclaimed fantasy series based on the idea of a flat earth:

Discworld is a comic (https://en.m.wikipedia.org/wiki/Comic_fantasy) fantasy (https://en.m.wikipedia.org/wiki/Fantasy) book series (https://en.m.wikipedia.org/wiki/Book_series) written by the English author Terry Pratchett (https://en.m.wikipedia.org/wiki/Terry_Pratchett) (1948–2015), set on the fictional Discworld (https://en.m.wikipedia.org/wiki/Discworld_(world)), a flat disc (https://en.m.wikipedia.org/wiki/Flat_Earth) balanced on the backs of four elephants which in turn stand on the back of a giant turtle....(Wikipedia)

Fall off the end? How would the flat earth move? What might happen to the sun?

Fall off the end? How would the flat earth move? What might happen to the sun?
On the back of elephants riding the Great Star turtle of course...