When to apply for change of status from B-2 to F-1?

I strongly suggest you talk to a competent immigration attorney before your file the change of status application to cover your bases.

My status is H1b visa Expired on Sept 2014, but a month ago I was applied F1 student & still in processing.

1) If you do not intent to study, I recommend you depart the U.S. and abandoned the application filed. I do not recommend filing staying in the...

May be you should address these questions to the company/ their attorney.

I have L2 visa, I am in US already .CAn I travel to different tourist cities in US along with my parent who has tourist visa.

Yes.

Can I renew my F-1 student visa?

Sorry to hear about your mother's sad demise. Unfortunately if you visa has expired, with a I-130 on file, it will be difficult to show a non...

B2 Visa, please some advice, my chances of receiving B2 visa are slim or none, I was previously a Gc holder, not anymore,

A private consultation is the best way to proceed in this case.

Can i go out of the country after L1 to H1B COS approved but before OCT, and reenter as B1/H4 visa to file COS to H1B again?

I do not recommend entering on one visa (namely B1/ H4) only for the purposes of entering and with an intention to work/ change status. There are...

Days present in the US before the re-entry permit and in progress to apply for citizenship

What is the longest gap she has, being away from U.S.? Did she seek to preserve her residency for naturalization? If yes, was it granted?

PERM got denied, chances of H1 extension

Your company's attorney will be the best counsel to advise the company regarding the next steps depending on the merits of the case.

How Layoff affects PERM application?

The relevant question is - was there a lay off?