My problem with Serial is that people listened to it and concluded some travesty of justice occurred. But the other side doesn't get to tell their side. Whenever you hear just one side of the story, you can be sure that the truth is significantly different.
This would make for a great case to see what the public opinion would be if he were to be released from prison, only later to have found out that he really did it. Reasonable doubt is tricky, it will let criminals off the hook because the police can not make a proper case.
Our justice system is supposed to require a high enough burden of proof that we don't convict innocent people, even if that means some guilty people aren't convicted as a result. Unfortunately, there have been, and still are, corrupt prosecutors out there that are more concerned with always getting a conviction whether or not there's enough evidence to prove the defendant is guilty.
I'm pretty sure he did it. But the state has an obligation here to ensure a fair trial and that's what they are doing.
I think that is very unlikely. I am not a lawyer, but I have never heard anything that indicates prosecutors have to present the same case upon a retrial. I imagine they will present a case with full knowledge of everything from Serial.