Yes, you can change the employer after your I-485 has been pending for more than 180 days. This is AC21. The new position should be similar or same to the one you got sponsorship for.
It doesn't matter if your I-140 has been approved by that time or not. AC21 requires 180+ day of pending I-485 only.
However, AC21 doesn't say a word about changing the position after I-485 is approved. So you have to stick with the sponsor (or whoever you end up with by that time) for some period of time. This way, USCIS will recognize your intent as "good faith" one.
It doesn't matter if your I-140 has been approved by that time or not. AC21 requires 180+ day of pending I-485 only.
However, AC21 doesn't say a word about changing the position after I-485 is approved. So you have to stick with the sponsor (or whoever you end up with by that time) for some period of time. This way, USCIS will recognize your intent as "good faith" one.
you are wrong you can change your intent after your i-485 is pending for more than 180 and i-140 is approved and your i-485 WONT be denied. It is called ac21.