Section 7. If any person in his answer denies the right of the petitioner to make the improvement or to take or damage his property, or to levy an assessment thereon, or impugns the validity or regularity of the proceedings, the court shall forthwith hear and determine the issue thus raised, and may order the petition dismissed or may enter an order establishing the right of the petitioner to take the real estate, or interest therein, described in the order for the purpose therein stated and to assess betterments as therein set forth, or may enter such other order as law and justice may require. If the court does not order the petition dismissed, and one or more of the respondents allege exceptions or appeal to the supreme judicial court or the matter is reported to the supreme judicial court, further proceedings shall not be stayed unless the justice who heard and determined the matter so directs. If no such issue is raised by any person in his answer, the court shall, on motion of the petitioner, enter an order establishing the right of the petitioner to take the real estate, or interest therein, described in the order for the purpose therein stated and to assess betterments as therein set forth. An order under this section establishing the right of the petitioner to take property or to assess betterments shall be final and conclusive as to the validity of the proceedings up to the date of the adoption of such order.