When Sam presents her project, she stands behind a desk at the front of the class. Immediately following, Carly comes in with her scooter and the desk disappears.
When Freddie and Carly are discussing their projects, presumably in the afternoon, they are wearing the same clothes they had on in class that morning. Freddie wheels his composting project in (including worms flown in Portugal). So somehow Freddie was able to complete his project on the same day it was assigned.
The power source material is referred to as "uranium". The container clearly shows in Cyrillic on the container "plutonium".
In the root and berry camp, when the teacher is looking outside of the tent, the stage lights are clearly visible on his glasses.