Revealing mistake: When Dylan is looking at the news articles in Thaddeus' cell, the camera pans over to one of the articles with the headline, "I am a victim": Thaddeus Bradley. The opening paragraphs on the first column are repeated throughout the entire article.
Revealing mistake: When the Horsemen are on the Thames after exposing Walter and Tressler, after Daniel introduces Dylan to the crowd as their leader, there is a shot of Daniel patting Dylan on the back. The shot then cuts to one of the crowds cheering. In this shot, three extras at the front of the crowd can be seen briefly looking at the camera as it passes by. The first is a man in a black coat, red scarf and holding a green glow stick, standing to the right of shot. The second is a woman in glasses standing beside the man. The third is a woman standing to the left of shot wearing a white hat. (01:48:50)
Answer: The only ones who knew the chip was fake were the Horsemen, no one else did. Walter did not know the chip was fake. The plan was to convince Walter that the chip was real so that they could lure him out of hiding with Walter attempting to kidnap and later kill them, and expose Walter to the public in doing so. They told the crowd after exposing Walter about the chip, because while it was a fake, they still had plans with it assuming it was real. If by "alert the FBI", you were referring to when Dylan gave the FBI director the evidence on Walter and Tressler, that was not the chip he gave to her, that was a hard drive containing all of Walter and Tressler's past dealings.
Casual Person