I have a pending application for a non immigrant status change from an F to a J visa. How long does it take to process it?

There is no set time for these applications. It is best to work with your DSO to assist you.

Is my green card still valid? can I go out and come back?

Generally your green card is no longer valid if you are outside of the US for over a year. I would not recommend any more trips outside the US.

You should make sure that your employer's immigration attorney is on board with all of these moves and you should be fine.

H-1B to B2 pending. If B2 is rejected, will it be a impact for future H4 application?

Every denial can have an impact on a future application. However since you are the dependent of your spouse you should be okay. If your B-2 is...

I have submitted all forms and documents to nvc in how many days i got an interview letter?

Things in Pakistan can take more time. Since it has been over a year you may want to hire an attorney to see what is going on with your application.

How long it takes to get your interview date .its been 3 weeks .since they updated my case to interview.

It can depend on many factors. Be patient and wait 30 days before calling USCIS

How long it takes the approval for I-765 Application for Employment Authorization in Philadelphia

About 3 months.

Can I AOS through marriage awhile my I918 is pending?

I agree with my colleague. Go ahead and file the paperwork but hire an attorney to avoid delays.

I just started a small business .

I agree with my colleague. No to both questions.

How long will it take for SEVIS to approve change of admission date for a college

The people at your DSO are in the best position to tell you how long it will take.