1)
What is "Yom Pokdi"?
1.
Radak: It is the day of the Ra'ash (earthquake), in the days of Uziyah.
2)
Will Hashem punish the Mizbechos?
1.
Radak: Yes. This is like "u'Veilohem Asah Hashem Shefatim" (Bamidbar 33:4).
3)
Why does it mention the corners of the Mizbe'ach?
1.
Radak: (a) When the corners fall, the Mizbe'ach falls, for the corners support the building, just like corners of the house. (b) They used to offer and throw the blood on the corners.
2.
Malbim: Hoshe'a cut off the corners, so people would not offer on them. This caused a rebellion among the nation.