What is "ve'Lo Yera'u Panai Reikam" coming to teach us?
Rashi #1: It teaches us the obligation to bring Olos Re'iyah and Shalmei Chagigah 1 on Sukos.
Rashi #2 (in Divrei Hayamim 2, 9:24) and Targum Yonnasan: It teaches us the obligation to appear in the Beis-Hamikdash with Korbanos - because it is not Kavod to appear before Hashem empty-handed (without a Mitzvah - Targum Yonasan)..
Seeing as the Torah has just been discussing Pesach, Shavu'os and Sukos, why does it mention them individually again?
Rosh Hashanah, 4b: To teach us that one is only Chayav Bal Te'acher after three Yamim Tovim 1 - a ruling which covers Chayvei Damim, Arachin, Charamin, Hekdeishos, Chata'os and Ashamos, Shelamim, Tzedakos, Ma'asros, B'chor and Ma'aser Beheimah, Leket, Shikchah and Pe'ah.