1)
What is conditional on David's sons guarding the Bris?
1.
Malbim: If they do, "Gam Beneihem Adei Ad Yeshvu l'Chisei Lach" (kingship will remain among them forever).
2)
What is the meaning of "v'Edosi Zo Alamdem"?
1.
Rashi: [They will guard My Bris and] this Edus that I will teach to them.
2.
Radak: There are no more Mitzvos to teach to them after Moshe! Rather, I will arouse them via the Nevi'im constantly, that they not forget the Torah.
