The flashback of Roslyn giving her necklace to JJ is shown twice, but their dialogue is slightly different the second time.
Symptoms of 23% of women diagnosed with schizophrenia manifest before age 19, so it is not rare in teenagers. Early symptoms include hallucinations (such as hearing voices), delusions, and disorganized thinking and speech; face blindness is not included in the list of symptoms. People with face blindness see faces (eyes, nose, lips), but they are unable to distinguish one person from another.
Fentanyl taken from a transdermal patch would not "knock you out instantaneously" as Garcia says. Those patches are designed to be slow release, while it begins to absorb right away the fentanyl takes up to 18 hours to reach a therapeutic dose in the bloodstream. If the contents of a patch were squeezed out and applied to a surface that someone touches, it would work a lot faster than it would in the patch, but even then it would take a good hour for the fentanyl to reach its peak effect.
The fictional town of East Allegheny PA is shown to be a small rural community in an aerial shot, but when pointing out the location of the abandoned train car on a map it is clearly a map of slightly south of Pittsburgh in an area that would both look more urban in aerial and is closest to the Monongahela river not the Allegheny.