Question 1 was a test question posted about ten years ago from this one (give or take about an hour). There's been a bit going on since then with the main forum. This post is a place for celebrants to respond with what they did. If others want to leave personal reflections on MathOverflow's 10th anniversary, answer posts on that are also welcome.
So how do you/did you celebrate MathOverflow?
Gerhard "The Party Isn't Over Yet" Paseman, 2019.09.28.