(a) To File. The defendant may file a motion for new trial before, but no later than 30 days after, the date when the trial court imposes or suspends sentence in open court.
(b) To Amend. Within 30 days after the date when the trial court imposes or suspends sentence in open court but before the court overrules any preceding motion for new trial, a defendant may, without leave of court, file one or more amended motions for new trial.