(1) A plea of not guilty may be withdrawn at any time prior to conviction.
(2)
(a) A plea of guilty or no contest may be withdrawn only upon leave of the court and a showing that it was not knowingly and voluntarily made.
(b) A request to withdraw a plea of guilty or no contest, except for a plea held in abeyance, shall be made by motion before sentence is announced. Sentence may not be announced unless the motion is denied. For a plea held in abeyance, a motion to withdraw the plea shall be made within 30 days of pleading guilty or no contest.