What was Lavan referring to when he said "Malei Shavu'a Zos"?
Rashi, Targum Yonasan and Rashbam: He was referring to the week of festivities (Sheva Berachos) 1 that Yakov was to complete before marrying Rachel.
Ramban: Refer to 29:21:1:4*.
See Ramban, who refutes this on the grounds that Sheva Berachos is a Takanah of Moshe Rabeinu, and was not yet instituted in the time of Yakov and Lavan, though he does concede that it may have been customary to perform it , particularly according to the Yerushalmi, which learns from here the principle 'Ein Me'arvin Simchah be'Simchah' (It is forbidden to mix two Simchos together), such as getting married on Chol ha'Mo'ed..
Why did Lavan speak in the plural (See Rashi) "And we will give you also this one ..."?
Ramban: He meant that the people, who would not allow him to marry off Rachel before Le'ah would now agree to give him Rachel.
Tosfos ha'Shalem (8, citing R. Efrayim): "V'Nitnah" is passive. It is as if she is already given to you. 1
Tosfos ha'Shalem (1, citing R. Efrayim): We will make a big party for Rachel, like we did for Leah.
Tosfos ha'Shalem (9): All people of the city will be guarantors for this.
According to the Ibn Ezra, "ve'Nitnah" is Nif'al (passive) - 'and there will be given to you'.
Having tricked Yakov once, wha made Lavan think tat Yakov would work for him honestly for aa second set of seven years, giving him Racherl on credit, to boot!?
Why did he immediately agree to work for another seven years for Rachel?
Why did he say "Gam Es Zos"?
Tosfos ha'Shalem (10): These are two inclusions, to include Bilhah and Zilpah. 1
He already gave Zilpah! Perhaps this is a hint that later, he will marry both of them.. (PF)
רש"י: ונתנה לך - לשון רבים: ממה בא רש"י להוציא?
גור אריה: אפשר לטעות שזה מלשון נפעל [ואז זה לשון עבר], ולכן פירש רש"י שזה לשון רבים.
רש"י: ונתנה לך - לשון רבים: למה לא אמר לבן 'ואתנה לך'?
גור אריה: דרך כבוד לשתף את שאר בני העיר.
גור אריה: כיוון שתלה בבני העיר ואמר "לא יעשה כן במקומנו" להקדים את הצעירה, לכן תלה גם כאן בבני העיר.