Like Isaac, Jacob was given food and wine (compare 27:25). He could not see in the darkness (compare 27:1). He became confused by clothing (compare 27:15) and misled by touch (compare 27:23).
The marriage had already been completed (the husband and wife had come together as one; 29:23; compare 2:24). Because of this, Jacob was bound to Leah.
It is not our custom here to give the younger daughter in marriage before the older: Laban's words are a reminder of what Jacob did when he, the younger son, pretended to be his older brother to gain the blessing (chapter 27). Now Leah, the older sister, pretended to be the younger sister to get a husband. God gave the deceiver a dose of his own deception as a discipline in his life.