Be it further enacted, That when twenty days shall have elapsed after final passage of a bond ordinance as provided by this Act, (a) any recitals or statements of fact contained in such bond ordinance, or in the preambles or recitals thereof, shall be deemed to be true for the purpose of determining the validity of the bonds thereby, authorized and the city and all others interested shall forever thereafter be estopped from denying the same, (b) such bond ordinance shall be conclusively presumed to have been duly and regularly passed by the city and to comply with the provisions of this Act and all other laws, and (c) the validity of such bond ordinance shall not thereafter be questioned by either a party plaintiff or a party defendant, except in a suit, action, or proceeding commenced prior to the expiration of such twenty days.