1)
Why does the Pasuk switch its expression here, from "Beini" (which appears in 9:12, 13, 15, 17) to "Bein E-lokim"?
1.
Rashi: It is referring to the Midas ha'Din (this is similar to Targum Yonasan and Ramban; refer to 9:14:2:2). 1
1
Though the Ramban maintains that Chazal's interpretation of Midas ha'Din (which Rashi is quoting) is different from the way Rashi presents it.
2)
Why should the mere appearance of the rainbow suffice to prevent the people from receiving their due punishment?