1) NAME CHANGES
QUESTION: The Gemara says that Avraham's name was irrevocably changed to Avraham from Avram. Similarly, a new name, Yisrael, was given to Yakov. Why was Yitzchak's name not changed?
(a) RAV NISIM GA'ON quotes the Yerushalmi (Berachos, end of ch. 1) which points out that Avraham's original name was given to him by his father, Terach. Yakov's name was given to him by his father, Yitzchak. Yitzchak's name, though, was given to him directly by Hash-m Himself (Bereishis 17:19). Therefore, there was no need to change it.
We may add that this also explains why the use of Avraham's original name had to be entirely discontinued, while Yakov's original name could be retained. Since Avraham's original name was given to him by an idolater, it had to be completely discarded. Yakov's name was given to him by a Tzadik -- his father -- and therefore it could still be used.
(b) RABEINU BACHYE (Bereishis 26:18) cites RABEINU CHANANEL who explains that when Yitzchak excavated the wells that his father had dug, he did not give them new names. Instead, he called them by the names that his father had given them (Bereishis 26:18). As a reward, his name was not changed.
Rabeinu Bachye adds that we learn from here the importance of following in the ways of our righteous parents and ancestors and clinging to the foundation they have laid for us even in seemingly insignificant matters.
2) IN WHAT LANGUAGE WAS THE TORAH SAID?
OPINIONS: The Gemara discusses whether the Torah was "said" in every language or only in Hebrew. To what Halachah is this question relevant?
(a) RASHI (Megilah 17b, DH b'Chol Lashon), according to the understanding of Tosfos and the Tosfos ha'Rosh, explains that the question regarding whether the Torah was said in every language or only in Hebrew is relevant to the reading of any of the sections of the Torah which the Torah obligates us to read (such as Parshas Zachor, the verses recited upon bringing Bikurim (the first fruits) to the Beis ha'Mikdash, and the verses recited by a woman performing Chalitzah). Even though the Mishnah in Sotah (7:2) says that these must be read in Hebrew, our Gemara is of the opinion that there are Tana'im who argue and maintain that these sections do not have to be read in Hebrew.
(b) The RITVA understands Rashi in Megilah as saying that this question is relevant to a Torah scroll written in any other language. Does it have the same sanctity as one written in Hebrew? (If it does not have the sanctity of a Torah scroll, then we may not read any of the Parshiyos from it, and it need not be treated with the same care as a Torah scroll.)
(c) TOSFOS (DH b'Lashon ha'Kodesh) and the RASHBA in the name of RAV HAI GA'ON explain that the Gemara is in doubt as to how the Torah was given at Sinai. Did Hash-m give us the Torah only in Hebrew, or in every language? (See also Tosfos DH b'Lashon.)
(d) The Ritva in the name of the RA'AVAD explains that the Gemara wants to know what language Hash-m used to teach the Torah to Moshe Rabeinu, and what language Moshe Rabeinu used to teach the Torah to the Jewish people. The Ra'avad adds that a practical ramification of this question is whether one must learn Torah, in our day, in Hebrew in order to fulfill the commandment, "You shall ponder the Torah day and night" (Yehoshua 1:8). If the Torah was taught to Moshe only in Hebrew, then one fulfills his obligation to learn Torah only when he learns it in Hebrew.