I have an already programmed STM32MCU. But I don't have the source code. I understand it is difficult to get the source code from the IC. I have heard some people can get the binary file from the IC which I can flash to another Arduino. Any guide or material will be helpful. I tried my luck with google. but didn't find any good resources on this matter.
you can download the flash content using a ST-Link probe and STM32CubeProg tool. you can't flash it to just "any" arduino board; it must be the exact same chip or same family MCU, if the IOs and peripherals used are the same.