Emergency question on H1B transfer

Currently I hold H1B visa, but will be laid off on 9/28. My H1B transfer is in process, specifically, waiting for the LCA to be approved. the last date for it(LCA) is 9/29 (the 7 days limit). Then the I-129 can be filed.

My question here is:
1) Begin from 9/29, if my I-129 can't reach the USCIS center, what status I am in then? Am I legal if I just stay in the USA?

2) If I-129 will be filed after 9/29, should I use premium process (I need to pay it by myself)?

3) After I get the receipt notice of the I-129,
Can I work for the new employer legally?
Or I just start work immediately when I-129 mailed out? Since there will be about 1 week mailing process for me to get the notice.

4) If my requested H1B get approved, but without new 1-94,
And I worked during the waiting period for the approval,
Can I get paid legally? Will the employer get any trouble?