1)
What does "Kadosh Yih'yeh" mean? What is it referring to?
1.
Rashi (like Shmuel, Ta'anis 11a): It means that the hair of his head 1 is holy, and he must therefore allow it to grow.
2.
Seforno (like R. Elazar, Ta'anis 11a): It means that the Nazir is holy, inasmuch as he abstains from his materialistic desires.
1
See Sifsei Chachamim.
2)
What is the meaning of "Pera Se'ar Rosho"?
1.
Rashi: It means the growth of hair on his head. 1
1
Rashi: Meaning a minimum of thirty days growth. This is similar to "Es Rosho Lo Yifra" (Vayikra 21:10).