The flashback from Prague shows surveillance cam with Hungarian language . The spoken language in Prague is Czech.
Agent Donnelly hands Detective Carter Brian Kelly's Certificate of Release or Discharge From Active Duty (DD214). Block 14 (halfway down the page, next to Carter's thumb) shows that he attended Defense Language Institute Foreign Language Center (DLIFLC) for 36 weeks to learn Modern Standard Arabic (MSA). However, the course is actually 64 weeks long; if he had been dropped after only 36 weeks, the DD214 would not indicate anything.
During a flashback to CIA-era John in Paris, the Machine's monitoring of him and his partner Kara highlights each of the agents...but John is highlighted with a yellow box - indicating he is aware of the Machine, despite it being three years before Finch ever contacts him and tells him of the Machine.