1)
Why does the Torah switch from Moshe and Aharon to Moshe (?Daber El B'nei Yisrael" ? in Pasuk #2) and then back to Moshe and Aharon ("u'Nesatem Osah" ? in Pasuk #3)?
1.
Oznayim la'Torah: Because it is referring to the Parshah of Parah Adumah which Hashem said to Moshe at Marah 1 with instructions that the people should give Moshe a Parah Adumah and that Moshe and Aharon should hand it over to Elazar.
1
As Rashi explained in Shmos 15:25. See Oznayim la'Torah.
