I filed an I-130 and it was approved for my husband.

For GC you will need an eligible sponsor.

Hello, I am a dentist from India. My wife is a US citizen. Our CR1 case is at NVC almost last stage. Waiting for my Interview.

I am not sure I can figure out where you are physically. If you are in the U.S., you may want to apply for adjustment.

Can a denied applicant apply for immigration again?

It depends who the USCIS considers to have misrepresented. Is the daughter a minor? If yes, she stands a good chance to have a new application...

What application are you talking about?

So your uncle filed the I-134 to support your stay? You cannot cancel it.

B-2 VISA extension applied and left USA before I-94 expired

A. no adverse consequence B. if you leave before I-94 expires, no consequence C. see above

Can it hurt me?

As long as you filed and paid taxes owed, you should be fine.

Can I get my parents by sponsoring their visiting visa with just a Valid I-94?

Tourist/ visitors apply for themselves at the Consulate. You, being in the U.S., can help out with sponsorship/ expenses.

Can I use an L1 visa to travel to the US only for a week or two for some business work?

I would go the other way around and use B1/B2 to do business and the other personal venturing.

I heard NPO jobs are h1b quota exempt. Being on H4 visa ,can i apply for NPO jobs and get a sponsorship for my H1B by oct 2013?

Not all non profits are cap exempt.