Part 2: What about animal sacrifices?

The sacrifices were meant to help the Jews remove themselves from practicing idolatry. Since the entire world worshiped through sacrifices at the time, the Jews would not accept a Torah without sacrifices. Therefore God instructed them to to sacrifice to him instead of the idols. (הרמב”ם מורה נבוכים ג, לב. חז”ל ויקרא רבה כב. החיד”א פני דוד ויקרא, אחרי מות קדושים. הרב אברבנאל ויקרא הקדמה, ועוד)

On mount Sinai, where the Torah was received from above, God did not include sacrifices. Only in the desert and not on mount Sinai did he do so. And more importantly, only after the the Jewish people sinned with the golden calf, which evidenced their continued attachment to idolatry. (האלשייך, ויקרא ז)

Sacrifices were therefore only included in the Torah after the sin with the golden calf.