In all such proceedings the court shall find whether the sale, conveyance or lease of such real property was lawful and valid. Upon the hearing of such case, the chancery court shall enter a decree validating and confirming the complainant's title to or leasehold or other interest in such real property as against the defendants in said suit, unless it shall appear to the court and the court shall find that the title thereto or leasehold or other interest therein was not lawfully and validly acquired by virtue of the sale, conveyance or lease under which such complainant claims, in which latter case the chancery court shall enter a decree annulling and cancelling such sale, conveyance or lease, or such other decree as the court may find to be lawful, just and equitable in such case. When any sale, conveyance or lease of any such property shall be confirmed and validated under the provisions of Sections 11-17-19 through 11-17-27 by decree of the chancery court, such decree shall forever estop and preclude the defendants and all other parties from thereafter questioning the validity of the sale, conveyance or lease involved in such proceedings.