1)
Why does it say "Al Mayim Rabim"?
1.
Rashi: These are other countries that you clouded them.
2.
Radak: Egypt grew on much water. There was much water in the rivers and lakes, aside from the great river.
2)
What is the meaning of "Sidlachem"?
1.
Radak: It is trampling.
3)
Will people never go there again?
1.
Radak: "Od" means for a long time, like "v'Lo Yasefu Od Gedudei Aram" (Melachim II, 6:23). Malbim - it will be desolate for 40 years (Perek 29).
4)
Why does it mention Behemah again?
1.
Malbim: Animals will not step in the water, nor on the ground outside.