Celeste Kane has long hair in all other flashbacks of being questioned about Lily's death, but in the scene of her being questioned at home, she has short hair.
Students can't reschedule AP tests. They're nationwide tests (given in May, generally) and are all done at the same time to prevent cheating.
When Veronica and Sabrina are talking in her house, the laptops have the dialog between Sabrina and her mother on them.
The screen of the tracking device which Veronica placed is the same in both episodes, despite being totally different vehicles: Hot Dogs (2005) (at 21.13), and in this episode (at 12.45).
In the scene where Veronica (Kristen Bell) visits Sabrina (Megan Henning) at her home, Sabrina and her mother, played by Lisa Long, speak Italian with each other. After her mother leaves and Veronica is sitting in her place, you can clearly see the Italian lines written on the computer screen in front of Sabrina.
Logan (Jason Dohring) claims he's been friends with Duncan (Teddy Dunn) since they were at kindergarten, yet back in episode 1.4, The Wrath of Con (2004), it was revealed Logan moved to Neptune when he was 12.