Yes, you can. You can use other information like the PA's first name and last name then passport number or city of birth. There are a bunch of combinations that you can try. Some people have their AORs arrive later, so they were able to link it before receiving an email.
It could be. You should receive an email stating that the sponsor is approved. There are some exceptions though.
It's good that you got a temporary file number. If your application package is complete after review, that number should become your permanent file number. It will then drop the X and will just start with an F.
Temporary = XF000******
Permanent = F000******
Yes. Same with some June 25 applicants.