1)
When is "Acharei Chen"?
1.
Rashi: It is after 40 years, like it says in Yechezkel 29:13. Malbim - that is when Malchus Bavel ceased.
2)
What is the meaning of "ki'Ymei Kedem"?
1.
Radak: It will not be at the level it was at from of yore, for it says "v'Hayu Sham Mamlachah Shefalah" (Yechezkel 29:14)! Rather, it will dwell in its land, like of yore.
