I know several unicyclists that drive a Fit. I can fit 3 - 36ers and 3 riders comfortably in mine. love it.
I don’t know if Sean was using 35mm or something bigger. Large format film adds a huge amount of “film pixels” over 35mm. If scanned at high enough resolution, the only new detail you’re picking up is the film grain. That largest version is probably like looking at the film with a microscope, but would be the best starting point if you were going to enlarge it even bigger.
As software continues to improve, it’s possible to reduce the grain and interpolate more pixels and really, really enlarge images if you have the patience to really work on them.
Some. You couldn’t make the 4x6" version into a poster, for example, but if you had the right software, you could upsize it at least one size with little or no apparent loss of quality.
Yes but digitally scanned 
@yeti- you can’t upres jpeg images, at least not for any kind of practical use. And when you purchase use rights of an image, you purchase them based on a size that you are going to use it for. Bigger=more$. This could cause problems if the buyer was trying to exploit that.