I had an interview 11/28/2012 in Colorado since then it has been almost 5 months and my status is still pending.

Nothing unusual about the checks, though I don't believe you asked a question.

Is it possible to expedite a "post activity decision" to fasten the visa processing?

If your brother is abroad, the files goes to the NVC. Unless your brother is aging out, this process cannot be expedited.

Any minimum period for L1B is needed to apply that extension

It will be in your interest if your employer starts the process early. They can file 180 days prior to the expiration of your I-94 card

Am I legally to do stock trading on H1-B Visa?

Yes

Can I change my status from a B-2 visa to an L-2 visa without going back to China? Is this allowed in the immigration law?

I agree with my colleagues. You can, though it is best to retain an attorney to represent you.

I've my H1b extension valid from 06/15/2013 and if I go for stamping, do I get stamping on my extension or current petition?

Visa is a travel document. As long as you have an approved petition, you can seek visa for that period to enable you to travel to the U.S.

Do I have to notify USCIS about this

It depends. You are to show residency for at least 3 months in the jurisdiction you apply.

With my 10 year green card can I live in another country and still receive US citizenship?

Once you apply and get approved for GC you are to maintain your residency. If you leave for long periods you will be considered to have abandoned...

So is it possible to submit the 9089 form with my old I-94 information now? Yes. It is current information while you stay in the U.S. Can we...

Am on L2 visa and EAD and work in Public School under County School Corp. My emp. wants to apply for my GC. What docs do I need?

Since the employer starts the process, it is best to seek referrals for a good attorney and seek his/ her representation towards the process. An...