Since when is a Chatas Chitzonah (whose blood is sprinkled on the Mizbe'ach ha'Olah) burned, - and not eaten by the Kohanim?
It was a Hora'as Sha'ah (a ruling for that time only Ramban). See Ramban, who explains the striking similarity between this Korban and the Chatas of a Kohen Gadol and why, whereas the blood was put on the Mizbe'ach ha'Chitzon, that of the Chatas of the Kohen Gadol was put on the Mizbe'ach ha'Penimi.
QUESTIONS ON RASHI
Rashi writes that this is the only case of a Chatas Chitzonah that is burned. Also Aharon's bull (Vayikra 8:14), the second bull of the Leviyim (Bamidbar 8:8), the Chata'os in the days of Ezra (Ezra 8:35) and in the days of Mashi'ach (Yechezkel 45) were or will be burned!
Riva: Rashi (Vayikra 9:11) wrote 'the only Chata'os Chitzonah that were burned were this (of Aharon) and the Milu'im.' Also of the Leviyim was Milu'im (to inaugurate them), and those in Ezra and Yechezkel. In Horiyos (6a), we say that it was a Hora'as Sha'ah. Here, Rashi means 'except for this, which was of the Milu'im, and similar matters.'
Moshav Zekenim: We can say that the second bull of the Leviyim was an inner Chatas, for they brought it for the Tzibur, and so we can say about Aharon's bull. 1