I am well acquainted with sprints and retros (I am accountant for an IT company). I think they are great tools for finding ways to improve the processes.
I would say that figuring out about keeping the threads open for shared questions is probably the best thing we learned. Especially as it was the first challenge of the season.
My suggestion coming out of this would be to include more examples, as you said, more clarity, to the rules and restrictions going forward. I believe a lot of what happened here was trying to decipher what was meant, and seeing other player's questions can sometimes point out the areas where we think we understand, but we actually don't. As per the gardening. My interpretation was it couldn't be done because planting was required to get to harvesting, and that would take more than 24 hours. I also didn't realize the yard sale table could be used to sell what we made or collected. I was thinking everything I made would be on different days, and would have to be sold the same day it was made. And using the yard sale table would be considered one activity, so it could only be used once. (These are just examples - I didn't even think about asking, because my thoughts seemed to make sense at the time).
Even if providing clarity and answering shared questions provide ideas about strategy, in the end I think it comes down to how well each player executes. Even if I knew everything exactly the top players were doing, I doubt I would ever execute as well as they do. It is just how I play, and I accept that.
All that being said, I learn so much from these challenges, especially ways to approach the game along with tips and tricks to work into my challenges and legacies. (Like photography being a good way to bring in extra money without having to buy a skills object, and it is a fast way to make friends. And the digital sketchpad, which I love already, but didn't realize how much I should be loving it.)
Thanks!