1)
Why did they say "Lashuv me'Acharei Hashem v'Im Leha'alos Alav?"?
1.
Malbim: "Lashuv me'Acharei Hashem" refers to intent for idolatry. "V'Im Leha'alos Alav?" is to offer Korbanos to Hashem on it.
2)
What is the meaning of "Hu Yevakesh"?
1.
Rashi: [If we intended to sin,] He will punish us.
