What did the bull come to atone for?
Rashi #1: It came to atone for all mundane activities and abominations that were (or would be) 1 performed on it.
Rashi #2 (citing the Toras Kohanim): It atoned for any stolen items that may have been donated regarding ythe work of the Mishkan and the Mizbe'ach.
Ramban (citing the Ibn Ezra): It came to atone for Aharon and his sons together with the two rams. 2
What does "ve'Chiteisa es ha'Mizbe'ach" mean?
Rashi: It means that Moshe was to place the blood of the bull on the Mizbe'ach with his finger.
What form did the anointing of the Mizbe'ach take?
Rashi and Targum Onkelos: Refer to 29:2:2:1*