Verifone VX 680 password TCP IP

I just bought an used Verifone VX680. This terminal used to run a custom application for a movie theater or something like that. They removed the software and cleaned up the terminal.

I need to develop an application for a delivery management system, nothing very serious yet.

After some time of research, I found that I have 3 ways to get this done:
1. Pay for some company to develop the system.
2. Pay (huge ammounts, relatively) for a framework and their services.
3. Get certified by Verifone to get access on the documentation and IDE, so I can develop my own application.

The third one seems to be the more sustainable, because I would develop my own application, in my terms. Besides the knowledge that I would acquire.

But I cannot find any information about this training. Only an email at the Verifone website that I cannot get any reply.

I'm aware that the application needs to be written in C++, it needs a specific IDE, a specific SDK and require a certificate to sign the files. But that's it.

I do not know anything else besides that and don't know how to get this info.