What are "Rosh Tzurim" and "Gevahos" referring to?
Rashi: "Rosh Tzurim" and "Gevahos" refers to their beginnings
What does "Hein Am le'Vadad Yishkon" mean?
Rashi (citing Targum Onkelos): It means that they are a nation who on the merit of their ancestors, will inherit the World to Come alone.
Rashi #2: 'When Yisrael rejoice no other nation rejoices together with them'. 1
Ramban: 'That they alone are as numerous as the dust of the earth, which nobody can count; neither can I count the four camps of Yisrael. 2
Rashbam: Refer to 23:9:1:2.
Targum Yonasan: 'They alone will inherit the world to come because they do not live the lifestyle of the nations'.
And what is the meaning of "u'va'Goyim Lo Yischashav"?
Rashi #1 (citing Targum Onkelos): And they will not be destroyed together with the other nations. 1
Rashi #2: And when the other nations have it good, Yisrael share in the benefits without detracting from their reward.