1. How to find out which real command line CodeBlocks uses for compiling?
Settings > Compilers and debuggers > Other settings > Compiler logging (Set it to Full logging).
2. I didn't confronte with this problem before moving from c:\MinGW to c:\develop\MinGW
Strange. May be the version detection code needs some clean-up. Did you change the Compiler bin path??
I guess C::B is trying to detect the compiler version. But the execution of GCC fails (probably due to the change in path) and the fall back code sets the version to 3.x. Because you shouldn't get this warning as this has been fixed sometimes back and C::B is now equipped to deal with it.