What stages do they have or how they do it I really don't know. Though it is known that one is screened extensively if there's military involvement or criminality issues. Those checks may take some time, 12-18 months or even longer in some cases.
I was in a queue for an interview (learned that from my GCMS notes) and that "queue" lasted for about 8 months. When our application exceeded average processing time we started sending emails.
you will see how they can help and what information they need from you in order to help you. (Your file number, client ID number etc.)
They are usually very well informed about immigration processes and willing to help.