Why did Yakov kiss Rachel when he met her? Why did it not constitute a lack of modesty?
Ramban: She was only a little girl. 1
Ramban (citing the Ibn Ezra): Neshikah with a 'Lamed' ("va'Yishak ... l'Rachel") denotes kissing on the hand or on the shoulder, and not on the mouth.
Seforno: Refer to 29:12:1:3.
Tosfos ha'Shalem (1, from Bereishis Rabah 70:12): It was due to kinship. Malbim
Why did Yakov cry?
Rashi #1: Because he foresaw that Rachel would not be buried together with him.
Rashi #2: Because, unlike Eliezer who arrived in Charan laden with gifts, he had come empty-handed. 1
Seforno: He cried because he did not merit to marry her in his youth, in which case he would have already had many children.
Tosfos ha'Shalem (2, from Bereishis Rabah 70:12): He saw people whispering to each other "he brought lewdness to here!"
Tosfos ha'Shalem (5): It was due to the afflictions of Yisrael and of Mashi'ach ben Yosef [which he saw through Ru'ach ha'Kodesh].
Rashi: This was because Esav sent his son Elifaz after him to kill him. Only, because Elifaz grew up on the lap of grandfather Yitzchak, took pity on Yakov, when he pleaded with him to spare his life. And, in order to carry out his father's instructions, he acted upon Yakov's advice, and took from him everything that he had with him - and a poor man is considered dead.
Why did Yakov love Rachel?
Mishnas R. Aharon 3 p.177: Yakov's primary Midah was Torah, the active power of speech. Rachel's primary Midah was silence, the passive power of speech.