LC filing during 6th year H1B - Implications of LC and I-140

[ninadt]

I am in my sixth year of H1B. My H1B will be expiring on 13th August 2013. I will get the extension on H1B (which includes recapture) till mid of june 2014 when I will complete my six years.
My employer will be in the position to file for my LC in or around September 2013. As per them, it will take maximum 10 to 12 months to get the LC approved and thereafter apply for my I-140.

I need advice about when I can file for 7th year extn and start working in following situations:
1. LC is approved and I-140 filed before H1B expiry
2. H1B is expired and LC is approved after that, I-140 is filed
3. H1B is expired, LC and I-140 are approved.

Also, for cases 2 and 3, what will be the implications if I go out of US after H1B expiry and what will be the implications if I changed my immigrant status to H4.

 

Please suggest. Thanks