The shot of the Las Vegas Strip was stock footage from Ocean's Eleven (2001).
Chloe admits to Lana that she lost her virginity to a fellow staffer at the Daily Planet during her internship. She names him as "Jimmy"; it's only later in the series that we confirm his surname is "Olsen".
While they are arguing, Clark refers to the necklace as red kryptonite instead of "red meteor rock," suggesting that perhaps Clark told Alicia of his true origins, but he was shocked that Alicia knew how it would affect him. How she knew is not explained. She simply tells him, "I know everything about you."
The red kryptonite ring that was in Chloe's drawer was taken by Clark in Exodus and was destroyed in the Clark-Jonathan battle in Phoenix, so it is unclear where this one came from, although she could have just got another one when she realized that the original ring had been taken.
Clark and Alicia's marriage was not legal since it would have been impossible to obtain a marriage license so quickly. Also, since Clark is 17, Nevada law would have required him to have either a parent or guardian present or written, notarized permission to marry. With no official document or legal permission, they probably just paid the church to simply perform a ceremony. At the end of this episode, Clark even acknowledges that it wasn't legal, and Alicia to her credit, never tries to act as if the marriage is binding once Clark rejects it.