At any time after filing the declaration, and within the period of four years thereafter, upon making satisfactory proof to the officer designated by the Secretary of the Interior of the reclamation and cultivation of said land to the extent and cost and in the manner aforesaid, and substantially in accordance with the plans herein provided for, and that he or she is a citizen of the United States, and upon payment to such officer of the additional sum of $1 per acre for said land, a patent shall issue therefor to the applicant or his assigns; but no person or association of persons shall hold by assignment or otherwise prior to the issue of patent, more than three hundred and twenty acres of such arid or desert lands, but this section shall not apply to entries made or initiated prior to March 3, 1891: Provided, however, That additional proofs may be required at any time within the period prescribed by law, and that the claims or entries made under sections 321 to 323, 325, and 327 to 329 of this title shall be subject to contest, as provided by the law, relating to homestead cases, for illegal inception, abandonment, or failure to comply with the requirements of law, and upon satisfactory proof thereof shall be canceled, and the lands, and moneys paid therefor, shall be forfeited to the United States.