Radak: The congregation of nations will stone them, like the law of adulterers. The Mashal is the bulwark that they built against the city.
2.
Malbim: They will sentence them to the four Misos Beis Din. The verse mentions stoning, the sword and burning
1
. It did not need to mention choking, for Stam Misah in the Torah is choking; it is the most lenient, and it is known that it is the punishment for adultery
2
.
According to Torah law, we can say that stoning is for adultery with Na'arah Me'urasah, the sword is for murder, and burning is for adultery of a Bas Kohen. (PF)
2)
What is the meaning of "u'Varei Os'hen b'Charvosam"?
1.
Rashi: They will be killed via the sword; this is a murderer's sentence. "U'Varei" is an expression of cutting, like "Har Yihyeh Lach? u'Vereso" (Yehoshua 17:18). Radak ? the Goyim will cut them with their swords; also Yonason translates so. The singular is used, for the Klal.