Why does the Torah tell us about the formation of Adam (in Pasuk 7) and subsequently, what Hashem did with him afterwards, when it already informed us about his creation earlier (See Bereishis 1:27)?
Rashi (citing the Beraisa of Rebbi Eliezer, the son of Rebbi Yossi ha'Gelili): This is the way of the Torah to relate something in general terms and to elaborate elsewhere, like we find later, where it repeats that Hashem formed the animals and the birds, to teach us that He brought the former to Adam for him to name them, and that He created the birds out of mud (a mixture of water and earth - and not out of water alone).
What is the significance of the Garden in Eden in which Hashem placed Adam, and when did He plant it there?
Rashi: Hashem 'planted' the Garden in Eden at this point, after the forming of Adam; He planted it on the east side of Eden. Its function will be described later in Pasuk 15.
Ramban (citing Targum Onkelus and the Midrash Rabah): The word "mi'Kedem" means (not in the east but) 'before the world was created'. 1 Consequently, when the Torah writes that "Hashem Elokim planted a garden", it does not mean that He planted regular fruit-trees that he brought from other locations. It means that, prior to the Creation, He created a place called Eden, in which He planted a Divine garden, with orderly rows of fruit that He Himself arranged. And those trees, which would never die, would continue to produce fruit forever. 2
This is also the opinion of Targum Yonasan, who adds that Hashem created Gan Eden for the Tzadikim.
In his commentary on the Ramban, Chevel citing the Maharsha, explains that the problem with Rashi's explanation is the fact that the Torah writes "Gan be'Eden mi'Kedem" and not 'Gan be'Eden be'Kedem' (or 'Gan be'Kedem le'Eden)?
What is the meaning of "mi'Kedem"?
Rosh: The Avos are called Kedem. The world was created for their sake.
Ramban: It means 'before the world was created'. Refer to 2:8:2:2.
רש"י: במזרחו של עדן: מה חידש רש"י?
גור אריה: רש"י בא לחלוק על התרגום שתירגם "מלקדמין", שהרי בפסוק ה' כתוב שהאדמה לא הצמיחה טרם שנברא האדם, וכן משמע מהפסוקים, "וייצר ה'... את האדם" ורק אח"כ "ויטע ה'...גן בעדן מקדם".
רש"י: הרי כבר כתבו וכו': קשה שהיה לרש"י להקשות כך בפסוק הקודם?
גור אריה: לפרוש התרגום קושיית רש"י לא קשה כי הפסוק עוסק בעבר- "מקדם", וכן יש לפרש "וייצר" וכבר יצר, אבל מכיון שרש"י דחה את התרגום יש לפרש כאן 'ויטע' עכשיו את הגן, וכן לעיל 'וייצר' עכשיו את האדם ויש להקשות שהוא כבר נברא.