Debug mode & Release mode

Dunno 'bout IAR.

You'd probably have to create separate 'Debug' and 'Release' Targets in your project?

Dunno 'bout IAR.

You'd probably have to create separate 'Debug' and 'Release' Targets in your project?

Yes.

I think there is no debug/release mode in KEIL.
In the debug mode, debugger use .obj files, and generate hex file in the state of release mode.

uVision always creates obj files;
There is an option on the output tab to create a hex file in addition

So you don't need to choose between Debug and Release - you get all the files all the time!
(the time taken to generate the hex from the executable is negligible).