Yes, you can request both reports anytime you want. If your reports cover the time frame that CIC wants, you can definitely use those reports for purposes like RQ.
Yes, CIC will tell you the reason for return. You can use the same payment receipt for re-submission. You don't have to pay again. Getting a refund from CIC is a different process.
Have you read the guideline document? If there is no instruction, then it's upto you how you start. In other words CIC doesn't have any preference. Hope this helps.
AOR is a formal letter that contains your client id, receipt number, number of applications (both adult and child), call center phone number. So, it's not just a print out from e-cas. It comes with the Discover Canada book.