1)
What is "Boser"?
1.
Rashi: It is unripe fruits. They set the teeth on edge.
2)
Why does it say "v'Shinei Vanim Tikhenah"?
1.
Rashi: The sons are stricken due to the fathers' sins. Radak - this is like "Avoseinu Chat'u v'Einam va'Anachnu Avonoseihem Savalnu" (Eichah 5:7).
