This camera is 2015 camera. CR2 is one of the options in the RAW menu. What is difference between CRW & CR2? Is it just the fact that in newer cameras the format is CR2. However this camera does not have native RAW ability. Can CR2 be read by the same apps that can read CRW? Thanks.
Changing the extension used by CHDK to save the file does not change the actual file itself in any way. All that changes is the file name. The RAW data (an unformated sensor dump) in the file is identical - if you want to test, change the extension and prefix to all available options and then use your favorite utility to compare the binary content of the file. They will all be the same.
The only reason for changing the prefix or extension is to trick Canon's PTP firmware and/or your PC's software into letting you upload the file from the camera to your PC.