I have approved Labor (PD - Jan 2007) and I-140 (Approved July 2008). I have I-485 Adjustment of Status pending (I-485 application done in Aug 2008). I have switched employer using my EAD(AC-21 not filed yet).For some inevitable circumstances I need to leave USA for good now. My question is, if in future I come back to USA on a new H1 with different employer and file for Labor, I-140 etc again, would I be able to retain my Priority date associated to old labor? (My previous employer has not revoke my approved I-140). Also, will this retention be possible in both of the following cases?
a) I come back to US past my old Priority date
b) I come back to US before my old Priority date