What is the significance of the fact that neither they, nor their fathers had known about the Manna?
Ramban #1: The fact that one can live on the supernatural Manna for a long period of time was a Chidush that neither they nor their ancestors would have conceived possible. 1
Ramban #2 (citing the Midrash Rabah): The Torah is pointing out the tremendous Chesed that Hashem had performed for the first time 2 by feeding them Heavenly grain, something that neither they nor their holy forefathers 3 had ever merited before. And this teaches us that, since Hashem can sustain man in whichever way He decrees, we should keep His Mitzvos in order to live.
See R. Chavel's notes.
Ramban: On the merit of Moshe.
Ramban: Despite the fact that they had followed Him in whatever He had commanded them - See Bereishis 12:1.
What are the implications of "Vaye'ancha, Vayar'ivecha Vaya'achilcha es ha'Man ... "?
Ramban #1, Da'as Zekenim, Hadar Zekenim and Rosh (in Pasuk 1): They all refer to the Manna. 1
Ramban #2 and Moshav Zekenim: "He afflicted you" - by leading you through the desert 2 for forty years; "He starved you" - at first; 3 "And He fed you the Manna" - after that 4 (thereby removing all toil and afflicton - Moshav Zekenim).
Sanhedrin, 99a: We learn, via a Gezirah Shavah "Vaye'ancha" "Samcheinu ki'Yemos Inisanu" - Tehilim, 90:15 - that the era of Mashi'ach will last for forty years. 5
Refer to 8:2:2:1 and to 8:16:1 & 2. See also Oznayim la'Torah who elaborates. Da'as Zekenim, Hadar Zekenim and Rosh (in Pasuk 1): As the Pasuk writes in Tehilim, 102:24 ? "Inah ba'Derech Kochi ... ". Because one cannot compare someone who has no bread in his basket to someone who does, as the Gemara states in Yoma 18b.
Ramban: As in Tehilim, 102:24.
See Sh'mos 16:3.
The Ramban proceeds to explain Pesukim 15, 16 in similar fashion. He concludes however, that although this explanation is more basic, his first explanation is the more correct one.
See Torah Temimah, note 1.
Why do we need to be told on what man lives?
Rashi (in Seifer ha'Pardes, 179): Because man lives, not on bread alone but on whatever comes out of Mouth of Hashem ... " hints at the B'rachah Achronah of 'Borei Nefashos'.
Da'as Zekenim, Hadar Zekenim and Rosh: To teach us thatt one should not place one's trust in food, rather, on what comes from Hashem's mouth - His Mitzvos which give life, in this world and in the world to come.
Peninim mi'Shulchan ha'Gra (Bereishis 1:29): Initially, vegetation would not have sustained man and animals. However, the last utterance of creation ("Nasati lachem es Kol Eisev? le'Ochlah") infused it with a nature to nourish and satiate them, as the current Pasuk concludes - "Lo al ha'Lechem Levado Yichyeh ha'Adam, Ki al Kol Motza Fi Hashem Yichyeh ha'Adam "
