Why does the Torah add "Chatas Hi" again in this Pasuk?
Rashi: To teach us that, if the Kemitzah and the Haktarah of a Minchas Chotei are not performed Lishmah, the Minchah is Pasul. 1
Sifra: "Chatas" teaches us that all its Avodos should be performed Lishman, and "Hi that, if the Kemitzah is performed she'Lo Lishmah, it is Pasul. 2
Why does the Torah not insert the words 'Re'ach Nicho'ach' here and by all Chata'os and Ashamos.?
Oznayim la'Torah (in Tzav, 7:5): Because they come to atone for a sin and it will suffice for them to do just that. The one exception is where the owner opts to bring a Se'irah and not a Kisbah. See Oznayim la'Torah there who elaborates.