Why is there no vowel under the Aleph in "Chotim"?
Radak: We find like this - "Korim El Hashem" (Tehilim 99:6).
What was the Begidah (betrayal)?
Ramban (Vayikra 19:26): Hashem did this great salvation for you today, and you ask [demons,] what is not Elokim?! (Refer to 14:32:6:3)
Alshich: Sha'ul rebuked those who told him, for not warning the people not to do so.
Malbim: You betrayed [the sanctity of] Kodshim.
What is the meaning of "Golu"?
Rashi: It is like Golelu (roll).
Here it says "ha'Yom". Verse 34 says that they slaughtered at night!
Rashi (citing Zevachim 120a) #1: They slaughtered Kodshim during the day, and Chulin at night.
Rashi (citing Zevachim 120a) #2: They slaughtered during the day Kodshim Hukdash to be offered on the public Bamah in Nov, and at night, Kodshim Hukdash to be offered on a private Bamah. This teaches that [such] Kodshim may be slaughtered at night!
Radak: "Ha'Yom" means at this time. They may not continue to slaughter like they have been. Also "Yom Tza'akti va'Laylah" (Tehilim 88:2) is the time I cried at night.
What was the purpose of the big rock?
Rashi: They would throw blood on it, and burn Chelev on it.