(2) The county treasurer shall cause the bonds to be delivered promptly to the purchasers upon payment therefor, and shall hold the proceeds of the sale of the bonds subject to the order of the district board to be used solely for the purpose for which the bonds were issued.
(3) When the bonds have been so executed, registered and delivered, their legality shall not be open to contest by the district or by any person or corporation for or on its behalf, for any reason whatever. [Amended by 1969 c.668 §27]