What license do I need and what is the difference between single and multicore license?
The license is due per device.
Multi Task means that the runtime runs on multiple processor cores.
Can the source code of a program be recovered by downloading it?
No, an installed program is available in binary form on the device.
https://revolution.kunbus.de/forum/viewtopic.php?f=12&t=2808
I am unable to connect to the device after an update of my code.
Basically logi.CAD 3 or the RTS will intercept a problem occurring at runtime (e.g. division by 0), unless it happens in a C block written by yourself. However, if you program "an endless loop" in the ST code - this will not be intercepted.You can then connect to the RevPi with tools like "Putty" and delete the file "RTSCode.so" there and restart the RTS.