From whom did he return the border?
Rashi: Malchei Aram had taken this region.
Radak: It was from Nochri kings who had taken it; we do not know who they were.
Yo'ash returned the cities! Why is this attributed to Yaravam?
Radak, Malbim: Yo'ash returned the cities that Melech Aram took. Yo'ash's son Yaravam returned everything (Malbim), i.e. "mi'Levo Chamas Ad Yam ha'Aravah" from [other] Nochri kings (Radak).
Did he only return land, or did he also conquer new land?
Radak: There are two opinions about this in Yerushalmi Chalah 2:1. It seems that he only returned, for mi'Levo Chamas Ad Yam ha'Aravah was conquered between Moshe 1 and Yehoshua. Also, it says "Heshiv"!
I do not know why he mentions Moshe, who never crossed the Yarden. (PF)
What Nevu'ah did Yonah have before this?
Rashi: He is the Navi who anointed Yehu [via Elisha's command] and said "Bnei Reva'im Yeshvu Lecha" (10:30).
Rashi citing Yevamos 98a: "Hashem's word to Yonah the second time" (Yonah 3:1) - He did not speak to him a third time, because Yonah was concerned for the son's honor, and not the Father's 1 . It says, "like Hashem said through Yonah"! Really, he did not prophesize about returning the border. Rather, "like Hashem said through Yonah" means that just like Ninveh was reversed from bad to good, also in the days of Yarav'am ben Yoash, Yisrael reversed from bad - Melech Aram made them like earth to be trampled - to good.
Radak and Malbim, citing another opinion in Yevamos 98a: Hashem spoke only twice with Yonah about Ninveh, but He also gave to him prophecy about Yisrael's border returning, like it says here.
Radak citing Pirkei d'R. Eliezer 10: He was concerned for Yisrael's honor, so he fled [to Chutz la'Aretz, which is not [normally] a place of prophecy]. He did not want Hashem to send him to Ninveh, for he knew that they are prone to repent, and there will be [prosecution against Yisrael, who did not repent, and] punishment for Yisrael. He was not concerned for Yisrael's honor, and not for Hashem's. (I.e. he feared lest Ninveh repent, and this will be bad for Yisrael, who did not repent. - PF)
