When I was teaching kids, in my Sunday School class we had a box that any kid could add a question to, anonymously. The only restrictions were that they had to be related to the Bible in some way. It's a great idea for Sunday School teachers out there.
Some of the questions that got asked have answers, I'm sure, but the Bible doesn't give them. Others may have many answers, and I don't claim to be exhaustive in the answers I give here. Hopefully, they'll help some of you out as well. The answers here are a bit more substantial than the answers given in class as the target audience is wider.