Best to consult with an attorney in private to explore options.

It depends on the court and your individual case. Contact the court for guidance.

No this is not considered a public benefit.

Check the individual country for business requirements.

Depends on the country you are traveling to and their visa requirements.

Generally 14-16 years until the visa becomes available.

Best to use the USCIS calculator to determine the proper filing fee for I751.

Generally in writing and by regular mail.

Yes you sister may request an extension before the I94 expiration.

Check the direct filing address on the USCIS webpage.