No this is not legal in the United States.

Depends on whether you were actually ordered removed.

You can contact USCIS directly to amend the error.

The sponsor should submit the I864 and the household member the I864A.

You can update this status at time of interview.

Yes you may begin the process by filing form I130.

You could attempt to reopen the case given the circumstances.

There are various employment options available. Consult with an attorney for guidance.

Rescheduled requests should take a few weeks to a month.

Contact ICE right away to report the failure to report and determine next steps.