The stones are mentioned five times near the beginning of the story and then five or six times more at the end. Why is their presence so important?

At the beginning of the story, the piles of stones look like boy play things. By the end of the story the stones take on a more menacing meaning, they are used to throw at the "winner" of the lottery.

By the way, your questions are too long, that's why they are not going through. Split your questions up and submit separately.