Nothing herein contained shall affect rights of action arising, or litigation pending, or orders of the Federal Trade Commission issued and in effect or pending on review, based on section 13 of this title, prior to June 19, 1936: Provided, That where, prior to June 19, 1936, the Federal Trade Commission has issued an order requiring any person to cease and desist from a violation of section 13 of this title, and such order is pending on review or is in effect, either as issued or as affirmed or modified by a court of competent jurisdiction, and the Commission shall have reason to believe that such person has committed, used or carried on, since June 19, 1936, or is committing, using or carrying on, any act, practice or method in violation of any of the provisions of said section 13 of this title, it may reopen such original proceedings and may issue and serve upon such person its complaint, supplementary to the original complaint, stating its charges in that respect. Thereupon the same proceedings shall be had upon such supplementary complaint as provided in section 21 of this title. If upon such hearing the Commission shall be of the opinion that any act, practice, or method charged in said supplementary complaint has been committed, used, or carried on since June 19, 1936, or is being committed, used or carried on, in violation of said section 13 of this title, it shall make a report in writing in which it shall state its findings as to the facts and shall issue and serve upon such person its order modifying or amending its original order to include any additional violations of law so found. Thereafter the provisions of section 21 of this title, as to review and enforcement of orders of the Commission shall in all things apply to such modified or amended order. If upon review as provided in said section 21 of this title the court shall set aside such modified or amended order, the original order shall not be affected thereby, but it shall be and remain in force and effect as fully and to the same extent as if such supplementary proceedings had not been taken.