1)
Why does the Torah insert the (otherwise superfluous) words "Vahishma Hashem be'Kol Daberhem"?
1.
Oznayim la'Torah: Becsause, in contrast to the other occasions, when Moshe needed to report to Hashem wht the people had said, Hashem heard their heartfelt request directly. 1
1
See Oznayim la'Torah.
2)
Why does the Torah insert the (otherwise superfluous) word "Heitivu Kol asher Diberu"?
1.
Oznayim la'Torah: Hashem justified both of Yisrael's statements: 1. "Ki Sochleinu ha'Eish ... " - Mi Yiten Vehayah Levavaam Zeh"; 2. "K'rav Atah u'Shema ... " Shuvu lachem le'Ohaleichem ... " - "ve'Atah Poh Amod Imadi Va'adbrah Elecha ... ".