Why does the Torah see fit to record all the details of the Avos, many of which are seemingly of minor importance, such as their travels from place to place, and the episodes of the wells?
Ramban: This is due to the principle cited in the Midrash Tanchuma, "Whatever happened to the Avos is a sign that it would later happen to their children." Ramban (as well as other commentaries) proceeds to interpret them, one after the other. 1
What does the Torah mean when it writes that Avraham "passed in the land"?
Seforno: It means that Avraham did not stop in any one place until Hashem told him to, as Hashem had instructed him (in 12:1). 1
This might also be what Rashi means when he comments that "he entered into it."
Why did Avraham go specifically to Sh'chem
Ramban #2: Avraham established ownership over Shechem even before Hashem gave him the land, 3 a hint that his children (i.e. Yaakov, see Bereishis 33: 18-20) would acquire it before the Kena'ani reached the stage that they were unworthy and had to be expelled from the land. 4 That is why HsShem ordered Avraham to acquire the land and to do various acts that would resemble things that were destined to happen to his descendants later. 5
Moshav Zekenim: Even much later, we find that Avraham said, "I am childless (i.e. I will not have heirs)!" (15:2). Initially, he thought that he will have children due to Tefilah. When he delayed to have children, he despaired.
Gur Aryeh: Otherwise, why did Avraham traverse the land until Shechem specifically? These events are recorded in Parshas Vayishlach (Bereishis 34).
In Pasuk 12:8, the Torah describes how Avraham pitched his tent between Beis-El and Ai, because [Ai] this would be the first place that Yehoshua would conquer in the conquest of Kena'an [excluding Yericho, which was conquered miraculously - Rav Chavel].
"What happened to the fathers is an indication of what would later happen to the children."
In similar vein, he explains how the Nevi'im would issue commands to their disciples or to kings to perform acts that allude to imminent historical events. As an example, he cites Yirmeyah ha'Navi, who ordered his disciple to take the Sefer that he had just written about the evils that would befall Bavel, read it, and then to tie a stone on to it and throw it into the river, adding - "so will Bavel sink!" (Yirmeyahu 51: 59-64) In fact, he explains, sometimes those acts not only indicated what the future had in store, but determined it.
Since Elon Moreh is another name for Sh'chem, what is the point of the repetition?
Rashi: Hashem showed Avraham Har Gerizim and Har Eival, where B'nei Yisrael made an oath to uphold the Torah [in the days of Yehoshua]. 1
Why was Sh'chem called "Elon Moreh"?
Targum Yonasan and Rashi (in his second explanation): "Moreh" means teaching, since that is where Yisrael accepted the oath of the Torah.
Ramban: "Elon Moreh" means "the plains belonging to Moreh." 1
This is like "Eilonei Mamrei" (13:18) means, "the plains belonging to Mamrei."
Why does Rashi emphasize that Hashem showed Avraham the location of Har Gerizim and Har Eival; why wasn't it sufficient to inform Avraham verbally?
Gur Aryeh #1: Hashem was showing Avraham the greatness of the Land, and its connection to the upper realms; there are locations in Eretz Yisrael that connect Above, whether for blessing or curse.
Gur Aryeh #2: The location itself was the catalyst for this prophecy; when Avraham arrived there, he received prophecy due to the great events that would take place there in the future.
What is the significance of the Pasuk "and the Cana'ani were then in the land"?
Rashi: Although the land had been given to Shem, the Kena'anim 1 were just then 2 gradually conquering it from them. That is why, in the following Pasuk, Hashem assures Avraham that He will return it to his children (who were the offspring of Shem). 3
Targum Yonasan and Ramban #1: The Pasuk is telling us that although the land was destined to go to the offspring of Shem, the time had not yet arrived for that to happen, and in the interim, the Cana'ani were living there. 4
Ramban #2: Having entered Cana'an without clear instructions, Avraham was afraid of the wicked Kena'anim. He therefore did not immediately build a Mizbe'ach, until Hashem brought him to Shechem, and promised that He would give him Eretz Cana'an. From that moment on, his fear departed and he built a Mizbe'ach and served Hashem publicly.
Moshav Zekenim: This cannot be, for Cham built Shechem for Kena'an (Sotah 34b)! Tzidon, north of Eretz Yisrael, was the northern border of Kena'an! Rather, it was of Kena'an; Shem was taking it, for Kena'an was his slave. Hadar Zekenim learns from "Ki Lo Shalem Avon ha'Emori" that it belonged to Kena'an! Rather, half was of Shem, and half of Kena'an. Alternatively, it was all of Kena'an; when he was cursed, it was [decreed that it be] taken from him when his sin would be complete.
Gur Aryeh: The implication of the word "then" (Az) is that it had not been the case previously.
QUESTIONS ON RASHI
Rashi writes: "Elon Moreh is one and the same as Shechem." How do we know this?
Gur Aryeh: The Pasuk does not tell us that Avraham went any further than Shechem at this point.