回复：重写一下，这样可能好回答一些，谢谢。

1. both require current PD
2. To file I-485 based on this I-140 when you already left the I-140 sponsor, the intent of I-140 sponsor to hire you still must exist. The burden of proof of such intent is on the petitioner and you. So, the proof you will provide is the promise to rehire/future offer in formal writing. And with the promise of future offer from the sponsor, 3. you don't need to do same/similar job and AC21 is not applicable to you. All you need to do is to work for the sponsor after GC approval.