(a) Any Formal Advisory Opinion issued pursuant to Rule 4-403 which is not thereafter disapproved by the Supreme Court of Georgia shall be binding on the State Bar of Georgia, the State Disciplinary Board, and the person who requested the opinion, in any subsequent disciplinary proceeding involving that person. Formal Advisory Opinions which have been approved or modified by the Supreme Court pursuant to Rule 4-403 shall also be binding in subsequent disciplinary proceedings which do not involve the person who requested the opinion.
(b) It shall be considered as mitigation to any grievance under these rules that the respondent has acted in accordance with and in reasonable reliance upon a written Informal Advisory Opinion requested by the respondent pursuant to Rule 4-40 1 or a Formal Advisory Opinion issued pursuant to Rule 4-403, but not reviewed by the Supreme Court of Georgia.