The mix of lengths will change from store to store. The lengths they receive is 6' through 12'. I'm sorry, I'm unable to fully answer your question.
I'll answer my own question. I went to the store and found that the boards were already exactly 9 feet. Perfect for my needs. I believe there were longer lengths, too, but I did not check those carefully.
Yes it is.
It is red oak or at least it is at my store. Think it is the same at all stores. The manufacturer will have to answer the question about chemicals.