1. The provisions of sections 64.800 to 64.906 are established as an alternative to sections 64.510 to 64.727 for counties of the second and third classifications, and as an alternative to sections 64.211 to 64.295 for counties of the first classification not having a charter form of government.

2. Except as provided in subsection 4 of this section, if the voters of any county of the second or third classification adopt county planning or zoning pursuant to sections 64.800 to 64.906 after having previously adopted county planning or zoning pursuant to sections 64.510 to 64.727, the provisions of sections 64.800 to 64.906 shall be effective in the county, and the county planning or zoning shall be conducted thereafter as provided in sections 64.800 to 64.906 rather than as provided in sections 64.510 to 64.727.

3. Except as provided in subsection 4 of this section, any county of the second classification which adopts county planning or zoning pursuant to sections 64.510 to 64.727 or 64.800 to 64.906 before becoming a county of the first classification shall continue to operate pursuant to those provisions as a county of the first classification until the county planning or zoning program is terminated pursuant to section 64.900. After the termination of county planning or zoning pursuant to sections 64.800 to 64.906, the county commission of any county of the first classification not having a charter form of government may exercise all powers and duties prescribed by and may elect to be subject to sections 64.211 to 64.295.

4. Notwithstanding the provisions of subsections 2 and 3 of this section, in any county of the first classification without a charter form of government which has a population of at least one hundred fifty thousand inhabitants which contains all or a portion of a city with a population of at least three hundred thousand inhabitants, and/or in any county of the first classification without a charter form of government with more than ^* eighty-two thousand inhabitants but less than eighty-two thousand one hundred inhabitants which has adopted planning and zoning prior to becoming a county of the first classification, the county governing body may, by ordinance, provide that the county’s planning and zoning may be conducted as provided in sections 64.211 to 64.295, sections 64.510 to 64.727, or sections 64.800 to 64.906.