2. The qualification of civil servants is a comprehensive issue. Since the Personnel Bureau, the Finance Bureau, the Provincial Public Security Department and the Municipal Bureau have all been trained, it shows that these three units have already accepted you, so you failed the exam, and it is impossible for the training school and any unit to cancel your civil servant qualification. If you don't know anyone from the Public Security Department, or you miss the exam, the Education Office of your provincial public security department may let you take the exam again, but it's as simple as that.
3. Training is very useful. I suggest you study hard and relax in your future work.