You have file number and your employer have some file number. After change employer you stay with old file number ,if you not change noc and professional. And time application from first day
I think, if you have express entry profile , you can make upfront medical. But you can't send me before request. And for way make upfront, if you can't send?)))
1) if you got AOR file number don't worry about date pnp certificate
2) if you wait AOR and pnp expired, you can ask province update certificate for next 6 months