A municipality is a Type A general-law municipality if it:
(1) has incorporated as a Type A general-law municipality under Subchapter A of Chapter 6 and has not acted to change to another type of municipality;
(2) has changed to a Type A general-law municipality under Subchapter B of Chapter 6 and has not acted to change to another type of municipality; or
(3) operated, immediately preceding September 1, 1987, under Chapters 1-10, Title 28, Revised Statutes, and has not acted to change to another type of municipality.