My father in law is a US citizen filed I130 petition for my Wife in June 2010 to my wife who is married and over 21 years

It is best if you retain a competent attorney to respond to RFE(s) of this nature. It will be money well spent. If you try to figure this out...

Can i submit multiple requests for h1-b transfer for multiple companies at the same time? And then chose one of the companies?

Prospective employers may petition in your behalf.

Have applied for B2 VISA Extn. thru ELIS for parents. Would it be OK to submit additional evidence while decision is pending ?

I don't see how it will help. When you filed for extension the reason was tourism. USCIS looks at the application on the date of filing and will...

Depends on how long your association with the company.

Invoking AC21-Is it safe

I don't see anything unusual and/ or cause for concern.

Will I face issues if my spouse worked without a valid EAD for over 180 days

I agree with my colleagues.

Do you have to be employed to maintain and renew your Employment Authorization Document?

How long has it been since the I-485 was filed?

Can I get a second OPT for an MBA after my MS in Engineering Management?

Did you use up all your OPT time on your Master's degree level. If yes, you may be out of luck!

Can I transfer my H1-B visa to a company that will hire me on a part time job, at a much lower salary.

It is in your interest to run by your business endeavors with an immigration attorney.

Filing H1B academic and green card NIW together

No.