1)
What Osos and Mofesim does this refer to?
1.
Radak: This is a Klal for the other Makos. They are a sign that "Kol Asher Chafetz Hashem Asah" (6). If the Makos were chance, it would not be that [all] the Egyptians were stricken and [all of] Yisrael were saved!
2)
Why does it say "b'Sochechi Egypt"?
1.
Rashi: This is like b'Sochech. Radak - it addresses Egypt. The Yud at the end is extra, like in "b'Sochechi Yerushalayim" (116:19); it makes the expression clearer.
3)
Was it only against Pharaoh and his servants?
1.
Radak: All the more so, among his nation! The verse teaches that even Pharaoh and his servants lacked strength to escape Hashem's desire.
