How long can you go to jail if you open someones elses mail?

yes it is. When you get a mail and it not address to you. I suggest you not to open it. cos of Feduarl law. however.. if someone not live there you need return that mail back to mail box with write...

Not unless it's an indecent picture.

Much will depend on the circumstances. The maximum is, in some jurisdictions, the death penalty. In other jurisdictions, the maximum could be life (or multiples thereof) with no parole. At the other...

Can it happen? Yes, it does. If you volunteer to take someone else's place?

yes it is because if it is not adressed to you i can tell you please do not open it