On the photo-sharing app Instagram, search the keywords #Fairfax, #Rockville or #DC and up pops hundreds of photos from children, The Washington Post reports. Among them, until recently, were many from Kyle, a 12-year-old. His full name, Gaithersburg middle school and favorite Montgomery County hangouts were on public display before his parents put a stop to it. Technically, Kyle was not supposed to be on Instagram, the mobile app owned by Facebook. The company’s policy sets the minimum age at 13. But Kyle said he was able to join easily, no questions asked. Within minutes of setting up his account this past fall, he was uploading “selfies” of his cherubic face and blond mop top and tagging photos of friends with their names…