Typically a novel is over 40k words plus, a novella is 15-40k words, and a short story is 15k or under. Depends on who you ask though: https://en.wikipedia.org/wiki/Novella#Word_counts

No, "typically" it's a "know-it-when-you-see-it" kind of thing. Trying to delineate precise word count boundaries is a misrepresentation of how these words are used. The numbers you gave are reasonable guidelines but are certainly not determinative.

That chart implies it is possible for somebody to write a work that wins the Hugo awards for best novelette and best novella, which I’d really like to see happen!