Can I apply for US citizenship 90 days before my 3rd year?

Yes, you can file 90 days prior to the 3rd anniversary.

Do I need to re-apply for my son petition again if I become a US citizen?

It will automatically be upgraded.

Does filing I-130 invalidate/cause issues in visitor visa ?

Not automatically. But a CBP officer may have doubts that they will leave since i 130 is filed.

Can I travel to the states frequently after filing for a K1 Visa to visit my Fiance?

It will depend on the CBP officer: to admit you or not.

What documents are needed to apply for a Change of Status from H4 to H1B ?

You should work with an attorney who was preparing your applications. The form that is used for change of status is I539. You can read instructions...

You should discuss this issue with an attorney of record for your case.

Can we file I-134 electronically to the United States consulate in Mexico?

Here is instructions to the form: file:///C:/Users/Alena/Downloads/i-134instr.pdf.

Good Day I have F4 Nigeria case with NVC my priority date is 03/08/2007, Last year i requested to change my priority date

Dear James, I am not sure based on what grounds you requested to change your priory date. I think you should consult with an attorney.

I-140 and I-485 are concurrently filed under EB1. Using I-140 EAD with adjustment pending status. How can I go back to H-1B

What status do you have now apart from "adjustment pending"? you should speak with your attorney, I think.

How is possible for me to get green card or long last visa to us as soon as possible?

There is no simple way for a parent of a US student to stay in the US with the student for many years. You should meet with a lawyer to see if you...