If the Judge took the plea and set off sentencing, then the Defendant must appear fro sentencing and is entitled to counsel. Any plea deal may be off the table for not appearing. The Court would be limited to any lawful sentence. I hope that answers your question.
You need to make an appointment with a medical malpractice lawyer. Usually initial consults are free. They will need more information to decide if you have a case. ie. Death certificate, medical records, etc. Good Luck.
You received a withhold of adjudication, meaning the case was not dismissed. That means you must have your record sealed for ten years before it can be expunged. The visa issue is something an immigration attorney needs to address.