You might find this thread helpful regarding GCKey regarding your second question:
https://www.canadavisa.com/canada-immigration-discussion-board/threads/how-to-link-my-application-to-my-account.696093/#post-8748059
Regarding your first and third questions, I would love to know the answers as well. For the first question, I think AOR1 arrives by email - I think I read it in another thread, although don't quote me on it. I can't find anything regarding the third question, so my guess so far is AOR1 is the first formal step.
https://www.canadavisa.com/canada-immigration-discussion-board/threads/how-to-link-my-application-to-my-account.696093/#post-8748059
Regarding your first and third questions, I would love to know the answers as well. For the first question, I think AOR1 arrives by email - I think I read it in another thread, although don't quote me on it. I can't find anything regarding the third question, so my guess so far is AOR1 is the first formal step.