How will Hashem stretch His hand against Edom?
Malbim: It will be via Nebuchadnetzar and the Chashmona'im, who eradicated from there people and animals.
Why will He make it desolate from Teiman?
Radak: I will destroy Edom from the side of Teiman. I.e. Teiman will be destroyed. Teiman is the Bechor of Elifaz ben Esav. His land is called on his name. So it says in Yirmeyah (49:7) "ha'Ein Od Chachmah b'Seiman."
What is "u'Dedaneh"?
Rashi: The residents of Dedan. Radak - the Hei is extra, for the accent is on the latter Dalet. (If the Hei were a pronoun, the last syllable would be accented.) Dedan is a great city in Eretz Edom. Also Yirmeyah mentioned "Yoshevei Dedan" (Yirmeyah 49:8).
Malbim: Dedan was under Edom's rule. They fell with them to the sword. The first time, Dedan separated from them - "Hemiku Lasheves Yoshevei Dedan" (Yirmeyah 49:8).
