background investigation

How long does a background investigation typically take? It's been two and half weeks since they started.

I failed a polygraph during an application process. I did tell them the truth and had nothing to hide. What is going to happen when I get to the background investigation stage for another department and they deny me for failing the previous poly test. What's the best way to address this?

I just had my background investigation, unfortunately I was denied for employment as a police officer. I wasn't given a reason why. Do I have a right to learn the specific reason for not getting the job?