Why does Moshe use the Lashon "Va'eschanan" rather than 'Va'espalel'?
Rashi #1: 'Chinun' is a Lashon one of 'a free gift', 1 (which means that Moshe was asking Hashem to answer him not as a reward for his good deeds). Even though Tzadikim are not short of good deeds, they only ask Hashem for free gifts. 2
What is the connection between this Parshah and the previous one?
Ramban: With reference to the "ba'Eis ha'Hi" in Pasuk 21, where, after discussing the defeat of Sichon and Og, Moshe prepared Yehoshua not to be afraid of the Cana'anim, he adds that he (Moshe) will not merit to enter Eretz Yisrael, since when he Davened, Hashem did not answer his prayers, but ordered him to strengthen Yehoshua.
What is the significance of "ba'Eis ha'Hi"?
Rashi and Ramban #2: After he had defeated Sichon and Og (nations that Hashem gave to Yisrael, and had distributed their land to two of the tribes - Ramban), 1 Moshe thought that perhaps Hashem had pardoned him and released the Neder (prohibiting him from entering Eretz Yisrael). 2
Rashbam: He did not Daven immediately when the decree was issued, due to the Mishnah in Avos, 4:18 'Al Tish'al lo be'Sha'as Nidro'. 5
Only his Tefilah that Hashem did answer (See Bamidbar 27:12 & 16-17), to which Moshe now refers in Pasuk 28.
Rashbam: As a reward, Hashem told him that, whereas other Meisim go to Gehinom, he would 'ascend to the top of Pisgah' and view it from there.
And why did Moshe add the word "Leimor"?
Rashi: This is one of three locations 1 where Moshe said to Hashem that he refuses to leave Him until He informs him whether He will fulfill his request or not.
Why did Moshe mention his (unanswered) Tefilah here?