Question regarding biological child on i751?

It is entirely to your advantage to disclose any child born into this relationship.

If I send my change of status from J1 to B2 a week before the program end date, would that be considered to be filed on time?

Yes, as long as CIS receives your application for COS prior to your program end date.

Can i get a visitor visa after serving 10 years ban?

Sorry, but US consulates rarely grant visitor's visas when one "overstayed" his/her previous visa and triggered the inadmissibility bar upon...

Asylum case?

You can safely fly out of the country after having withdrawn your application for asylum. There are no immigration controls when departing.

I'm waiting for a H1B answer, my sponsor propose to take the premium process, but ask me to pay for it. Is it normal ?

Yes, that could be construed as normal, given that PPS is not a requirement, but simply an option, which if you insist on it, the employer can ask...

For the form I-485, if the question states "if any" or "if different from above" then do you need to fill in "None" or "N/A"?

Either way will work in this instance.

H1B extension is denied and refile?

You cannot continue working after the expiration of your I-94.

I agree. A "one time" is OK. Multiple and recurring such "referral fees" will have the effect of making it a "business", tantamount to...

I have a plied for naturalization but my green card expire what should I do

Simply wait for your N-400 interview to be scheduled. There is no need to apply for a new GC at this stage.

I've recently sent a letter to uscis cancelling a petition however I no longer want them to cancel what can I do?

A cancellation notice cannot be "taken back" - need to pay the fee again and file a new petition.