1)
When did Chaza'el come to fight?
1.
Rashi (from Tanchuma Mas'ei 12): This was after Yehoyada died, and Yo'ash made himself an idolatry. Radak - so it says in Divrei ha'Yamim II, 24:17-23. They killed Zecharyah, Yehoyada's son, via the king's command, for he rebuked them. The next year, Chaza'el came. There were two wars. The one here was first.
2)
Gas was of Pelishtim! Does the verse teach what Chaza'el took from Pelishtim?
1.
Radak: It belonged to Malchei Yehudah; David had captured it from the Pelishtim.
