Legal Question in Appeals and Writs in California

Re: writ of error coram nobis?

No. The Federal rules have no effect on state procedures.

Coram nobis (when addressed to trial courts) and coram vobis (when addressed to appellate courts) are writs almost always for criminal cases. But they have been used in civil cases.

These are highly technical terms and procedures, limited in their proper use.

Re: writ of error coram nobis?

Only in the federal courts, not in state courts. The federal rules govern only the federal court system. California still recognizes coram nobis. I don't know which other states still do, but whether to do so is up to them..