Changing employer with approved I-140 through consular processing

[vcboss]

Hi, I live and work in USA but my employer filed for my NIW and I-140 through consular processing. My priority date is 22 Mar 2024. I now have an approved I-140 and would like to change employers. I have consulted with 3 lawyers and am getting conflicting responses. Can I utilize AC21 rule after 180 days of approved I-140 or do I absolutely need to have I-485 pending for 180 days? One lawyer stated that even if I don't have an I-485 pending, after 180 days even if my employer withdraws the I-140, I will still maintain my priority date. Is that true? Can I apply for my own I-485 without my employer/petitioner knowing about it? My potential new employer is willing to apply for another NIW or PERM if needed.