Audio problem: In the beginning, Claudette and the other counsellors are all singing. When they get closer you can see that Claudette is playing the guitar, then she stops, but the guitar playing and singing still continues. (00:02:10)
Audio problem: When the kid is playing classic guitar the movement on the guitar's neck doesn't match the music. He somehow manage to play high tones on low frets. (00:36:45)
Audio problem: Annie walks over to a dog and says "Hi girl! Excuse me, hi boy!" Her lips don't move correctly to the line "..Excuse me.." (00:07:00)
Answer: 1. She was most likely hanged. 2. Mrs. Voorhees wasn't possessed by Jason. She simply went insane when Jason drowned and wanted revenge. 3. He's not burnt, only disfigured.