In order for a member to be eligible to receive retirement benefits under this chapter, he must meet the following requirements:

(1) The member must have served a minimum of at least four years as a qualified and commissioned sheriff of a county in the State of Georgia during which time the member served as sheriff of the superior court of that county after and including January 1, 1961; provided, however, as applied to any person first or again becoming a sheriff and a member on or after July 1, 1988, the member must have served a minimum of at least eight years as a qualified and commissioned sheriff of a county as provided in this paragraph;

(2) The member must have paid dues as required by this chapter;

(3) He must have reached the age of 55 years, provided that any member who is otherwise eligible to receive retirement benefits except for his having reached the age of 60 years shall, from and after April 1, 1973, be eligible to receive retirement benefits upon reaching the age of 55 years, even though he may have ceased to hold the office of sheriff;

(4) He must have terminated his official capacity and service as a sheriff;

(5) He must have filed and received approval of such application for retirement benefits as may be required by the board. The application shall be filed with the secretary-treasurer within a period of 90 days, or as soon thereafter as possible, after reaching 55 years of age or after termination of his official capacity and service as a sheriff, whichever is the latter date; and

(6) He must have fully complied with all mandatory provisions of this chapter and rules and regulations adopted by the board.