When Kenneth and Darius are at the camp and Darius asks what kind of musical instrument Kenneth has, he responds that the instrument is a zither. The instrument they are using is a mountain, or Appalachian, dulcimer. Mountain dulcimers do fall into the general zither category, but typically when people refer to zithers they mean instruments that have shorter scale lengths and many more strings, or courses, than mountain dulcimers. Calling a dulcimer a zither is like calling a viola or cello a violin simply because they fall into the general "violin family" category.
When Darius and Arnau are sitting and watching the mailboxes, you can clearly see a Stock Sticker and a "Safety Checked" sticker on the windshield of the Escalade. Later at 14 minutes, when Jeff is going to meet Kenneth, the stock sticker is missing, but the safety check one is still present.
When Darius is backing up the van to pick up Kenneth during the laser robbery, it is obviously a shot of the van driving forward (used a few shots later), but run backwards - exhaust goes into the tailpipe.