From my understanding we cannot even begin to request police reports for the principal applicant on a PR application until an official request letter is given to us. In our case my wife has lived in various Asian countries over the years and she is currently residing in Singapore so this would mean after i am approved as a sponsor the Singapore office would receive the file, they would then issue her this official letter (or letters) in which she could use to send along with her requests to all the countries where she has lived in?