Section 28A. The provisions of sections sixteen to twenty-eight, inclusive, shall, so far as apt, apply to regional school districts established under the provisions of section fifteen of chapter seventy-one, but the provisions of section sixteen relating to the countersigning of bonds and notes, the provisions of section 21C relating to lease purchase financing agreements and the provisions of section twenty-four relating to the countersigning and approval of notes and the certificates of the clerk relating thereto shall not apply to such districts.