Why does the Pasuk say "Ki Ani Hashem Elokeichem" before commanding Yisrael to be holy?
Rashi and Seforno: The Pasuk means that Yisrael should follow in the footsteps of Hashem
and be holy,
just as He is holy.
Tosfos (Hadar Zakeinim): If a king is holy, it is befitting for his servants to be holy like He is.
In keeping with the Mitzvah to go in the ways of Hashem ("ve'Halachta bi'Derachav" - Devarim 28:9
And why does repeat "Vi'heyisem Kedoshim"?
Rashi: The Pasuk is saying that if you comply and live with Kedushah, then Hashem will sanctify you in Heaven and in the World to Come.
Why, in the current Pesukim, does the Torah issue a number of La'avin with regard to eating Sheratzim?
Rashi and Ramban (on Pasuk 41): To render someone who eats them Chayav a number of La'avin, depending on the type of Sheretz.
As the Gemara states in Makos, 16b 'Someone who eats a Putisa (a water-insect), is subject to four Malkiyos, an ant, five, and a hornet, six (Rashi).