I am wondering if you are a little confused about all the acronyms being used here... which I could see why!!
AOR= Acknowledgement of Receipt People can get this, usually as email, anywhere between I think like a month to four months after sending in their application. It is basically just CIC saying we received your application and it seems to be in order. Some people don't get AOR at all. Some people with or without AOR can log into Ecas - there really is no rhyme or reason.
AIP= Approved in Principal This is first stage approval from CIC and basically means CIC believes your relationship to be genuine and will now look move into looking at stage 2. Right now it takes about 17 months to get AIP - although this timeline is increasing all the time!
DM= Decision Made This is stage 2 approval - where the final decision has been made on whether the applicant has been accepted as PR or not. Some people have been waiting a year (after AIP) for this and others are getting it within weeks - again no rhyme or reason!
Landing Interview= This is the final step. It's less of an interview and more of a last step where the applicant has to go to their local CIC office and there they are asked a few questions and are approved PR. The PR card is sent after that.
Not sure if it helps but thought I'd try
. If I made any mistakes here the multiple people here who have more knowledge than me - please let me know!