Need help - L2 to H1

[Simby2008]

I was on L2 visa and was working for a company A on EAD. Company B filed my H1B in April,2007 and luckily it got selected in the lottery. My H1-B was approved with a "Change of Status" effective 1st Oct, 2007.
I was working on L2 EAD till Dec,07 on a project with company A and joined company B in Jan,2008. My husband was maintaining valid L1 status throughout this period.

1) If H1 is approved with Change of Status, is it mandatory to join the H1 employer starting 1st Oct,07 or is it optional for me to join the H1 employer anytime as I was holding L2 EAD and was working with company A.
2) Does my status automatically change from L2 to H1 starting 1st Oct,07 or will i be considered on H1-B only the day I join the petitioning employer.
3) Am I allowed to work on L2 EAD even though I have an approved H1B petition effective 1st Oct,07 and can I join the petitioning employer at a later date.

Thanks alot

[DMX17]

1) It's mendatory (unless you travelled and came back after Oct 1st on L2).
2) Yes. The status changes to H1 on Oct 1st.
3) Not unless you travel and come back on L2 status.

Basically, your work for the L2 employer without proper authorization was illegal. On Oct 1st, your status changed to H1 and you should have joined the H1 employer OR transferred the H1 to the L2 employer.

Did you travel at any point?

[txh1b]

https://www.immihelp.com/h1b-visa-change-of-status-faq/