Woohoo

I just had a second thought and it was right!! The app ID cannot contain the numbers, so instead I changed the app ID to com.onyx.kreaderold
Could you try the attached old app on the new firmware? I renamed the UI visible name to "Neo Reader fw 2.0.1". When you install it nad you try to open any pdf the lanucher should ask you which app to use. Be sure to select "JUST ONCE" so the next time the launcher ask you again.
The attachement is zipped, just unzip before copying to the reader.
NeoReaderFw2.0.1.apk.zip