All legislative steps and all improvements and assessment proceedings taken by any charter municipal corporation prior to April 16, 1925, which would have been valid if this section and section 701.05 of the Revised Code had been in effect at the time, shall be legal and valid legislative steps, improvements, and assessments. All notes or bonds issued or authorized by any such charter municipal corporation prior to such date, which have been or will be sold for not less than par and accrued interest, and the proceeds thereof have been or will be paid into the treasury, which would have been valid if such sections had been in effect at the time, shall be valid and binding obligations.