1)
Why does the Torah change from "Yadcha" (singular) in Pasuk 18, to "Yadav" (plural) here?
1.
Rashi: To teach us that Moshe transmitted to Yehoshua generously, much more than what Hashem instructed him to ? Hashem told him to place one hand on Yehoshua, and he placed two hands! 1
1
Sanhedrin, 105b: And we learn from here that a person is not jealous of his Talmid. See Torah Temimah, note 32, who elaborates.
2)
Why does the Torah add the words "Ka'asher Diber Hashem"?
1.
Rashi: To teach us that Moshe also carried out the command "ve'Nasata me'Hodcha alav".