Is there a change log or something of the sort? I am actually half way through chapter 4 and looking back I see some differences between what I've already done

Is there a change log or something of the sort? I am actually half way through chapter 4 and looking back I see some differences between what I've already done and what is presented on the site, just want to make sure I'm either not missing things or what I've already written is ok to continue with.