To which goat is the Pasuk referring?
Rashi, Seforno, Rashbam (citing Zevachim, 101b) and Targum Yonasan: It is referring to the goat of Rosh Chodesh Musaf. 1
Why was it burned?
Rashi #1: Because it came into contact with Tum'ah. 1
Rashi #2 and Targum Yonasan 2 : Because Aharon and his sons were On'nim.
What is the significance of the double Lashon "Darosh Dorash Moshe"?
Rashi: Moshe wanted to know why the one was burned and why the others were not eaten.
Why did Moshe address Elazar and Isamar and not Aharon?
Rashi: In deference to Aharon he turned towards his sons and vented his anger. 1
Even though in fact, he was equally angry with Aharon, since all three had burnt the Chatas.
Why does the Pasuk add the word "Leimor"?