Who eats their sacrifices and drinks their libations?
Rashi: The gods mentioned in the previous Pasuk to which they sacrificed.
Ramban, Rashbam, Targum Onkelos and Targum Yonasan: The G-d of Yisrael.
Why does the Torah refer to the gods that Yisrael worshipped in the plural - "Yocheilu" and "Yishtu"?
Ramban: The enemy has many gods, so they use the plural also for the G-d of Yisrael. 1
Ramban: Hence Hashem responds in the next Pasuk] "Re'u
What are the ramifications of "Yishtu Yein Nesichm"?
Avodah Zarah, 29b: It teaches us that, just as "Cheilev Zevocheimo") is Asur be'Hana'ah, so too is "Yein Nesicham" (Yayin Nesech). 1
See Torah Temimah, mnote 81.
What are the implications of "Y'hi aleichem Sisrah"?
Rashi: Refer to 32:35:5:1*
Rashbam: If He is capable of helping you, 'Let Him conceal you in his shade!'