All laws and parts of laws relating to pensions, retirement, and relief funds for policemen, firemen, and other employees of the city, contained in the general or local laws of the state, as the same may apply and be in effect with respect to any city at the time when such city shall elect to be governed by the provisions of this chapter, shall continue in full force and effect, and without interruption or change as to any rights which have been acquired thereunder, after adoption of the mayor/commission/city manager form of government by such city.