1)
How could Moshe be certain that Hashem would answer him?
1.
Rashi: This conveys Moshe's greatness, 1 in that he was like a Talmid who knows that his Rebbi will always answer his questions. 2
1
See also Ki Sissa Sh'mos, 32:30 and Rashi in ve'Zos ha'Berachah Devarim, 34:10.
2
Rashi: Praiseworthy is the son of man who is able to communicate with the Shechinah whenever he wants to!
2)
What are the implications of the (otherwise superfluous) word "Asher Yetzaveh Hashem lachem"?