Question on AOS portability and GC processing time

I would like to know if I-485 applications are processed as per receipt date or as per priority date? My I-485 was filed in 2020 and my priority date is in 2014. As of the current situation, USCIS processing time is pretty close to 2020 October, but my priority date is not current. Considering my I-485 is already filed, would 485 be approved based on the receipt date, or it will stay pending and only be approved once my priority date becomes current again?

I would also like to get some clarity on AOS portability. My I-140 was earlier filed with a Software Engineer role under SOC code 15-1132 in 2014. I transitioned to management role in 2020. My I-485 was filed in Oct 2020 where the recent manager job title was added. If I am changing my employer at this time, do I need to make any amendments in the current application? Or is it ok to move to the new employer with AOS portability to management role?

I-485 will only be approved once your PDF is current and your file is documentarily completed, for e.g. all RFEs answered, biometrics & medical submitted.

As long as the new job offer is in the same or a similar occupational classification as the job offer for which the Form I-140 petition was filed, the new employer can simply file I-485J to take over your GC process.
Your employer may still be able to justify your job title change if it was a career progression with most duties being same as the job position in your I-140.
Consult an immigration lawyer to make sure you don’t face any issues with your AOS later on.