1)
What is the "Cheilev ha'Chatas" referring to?
2)
Why does the Torah not specify the Par and the Sa'ir, like it will in Pasuk 27?
1.
Oznayim la'Torah: Because "Cheilev ha'Chatas" incorporates that of the Sa'ir of Musaf, which hasn't been mentioned yet.
3)
On which Mizbe'ach did they burn the Cheilev ha'Chatas?
1.
Rashi: On the Mizbe'ach ha'Olah. 1
1
It cannot be on the Mizbe'ach ha'Ketores, since we learned in Ki Sissa Sh'mos, 30:9 that anything other than the Ketores may not be offered on it (Rashi).
4)
We already know that the Cheilev of a Chatas is burned on the Mizbe'ach. Why does the Torah need to repeat it here?