You can sign up at Nanowrimo website to have your final word count verified, and become an official winner. Sign up was free the last time I checked.

As for posting, do what you feel comfortable. I've seen fanfic writers post links to their project on the appropriate fandom comms. My writing is very rough at times so I keep it on my computer. If you have plans to publish the work, don't post it. No plans, and want to share then go for it.