You told me this PERM is void and your new employer need to file another PERM for you.
(1) Can I change the job using the current H1-B?
-If you still work for the same employer with different job responsibilities from your current job, your employer needs to file the H1 amendment (if just the job title change/promotion, do nothing). If you change your employer, your new employer needs to file the H1 transfer.
(2) I have to start from the very beginning if I change my job. This is what I understand from your reply. Is that correct?
-Correct even if it is only the job title change.
(3) If I get my PERM and file I-140 form and they are processing the I-140, what should I do if I get another job?
Do I have to file a new PERM and file a new I-140?
-Yes unless you will come back to work for the same employer with the same position.
Thanks a lot.
