1)
When did they test Hashem and rebel against Him?
1.
Rashi: In the days of the Shoftim [Radak, Malbim - this was after Yehoshua and the Zekenim died].
2)
How did they test Hashem?
1.
Malbim: They again doubted if He is Elokim Elyon, the Cause of causes. This is why they served idolatry - they thought that Hashem is only one of the individual powers that rules over the land.
3)
What are "Edosav"?
1.
Malbim: They are what the Nevi'im testified about, and also testimonies of punishments of the Torah.