What are the implications of "v'Kam ha'Bayis ... la'Tzemisus"?
Rashi: It means that if the seller did not redeem within the year, his permanent rights in the house go to the purchaser, and the house becomes his forever.
What is the significance of the fact that the word "Lo" is spelt with an 'Alef' and pronounced with a 'Vav'?
Rashi: It teaches us that, even if the town is not currently surrounded by a wall, it is considered a walled town if it had a wall around it in the time of Yehoshua ben Nun. 1
As if to say, 'It doesn't have a wall, but it did'. Rashi: The Torah ought really to have written "Lah" (with a 'Hey'), seeing as "Ir" is feminine, and it wrote "Lo" with a 'Vav', because it has the same sound as "Lo" with an 'Alef'. Hadar Zekenim
Why does the Torah add "Lo Yeitzei ba'Yovel", which is seemingly superfluous?
Rashi (citing Rav Safra, Erchin 31b): To teach us that even if Yovel occurs during the first year, the house does not revert to the seller.
What is a Temimah (full) year?
Moshav Zekenim (from Erchin 31b): Rashi says that it is 365 days; Rabanan say, it is a year from day to day; if it is a leap year, the extra month is included. 1
Moshav Zekenim citing R. Vardimus: This is only because it says "Temimah". If not, it is 12 months, and the buyer would not get the added month. Therefore, the added month is included in the 24 months of nursing. "Lo Sevashel Gedi ba'Chalev Imo" hints to this. (I did not understand the hint, Some learn from the verse two years of 365 days; refer to Shemos 23:19:5:9 and the note there. - PF)