Does it says INVALID_ARGUMENT or INVALID_SIGNATURE?
If it's the first one you didn't got the ''Done'' line.
If you have the second one, your CIA is not legit. :p
The chances of downgrading succesfully are around 95% if you choose the correct files and you follow the tutorial correctly (that doesn't mean it will erase the 5% chances of bricking. :p)
auto
It's actually quite fun. Completed it in 1 week, I had lots of fun designing the houses. :p