Continuity mistake: When Reese pushes off the table, he knocks one of the place mats out of place. In the next shot, it is where it's supposed to be. This switches back and forth in the scenes. (00:01:27)
Revealing mistake: When Kristen starts taking her helmet off you can see her hair is actually a wig.
Answer: Francis is only allowed to talk on the phone at school for three minutes a day. I think the code gives him free access to talk to his girlfriend.