can we get the code from the robot controller and work with it in the mplab?
Not really.
While you can retrieve a program from the RC, what you end up with is the raw numbers which comprise the code, equivalent to the output from an assembler or compiler. It’s theoretically possible to “disassemble” a .hex file into assembly language, and even more theoretically possible to turn that into C source code. However, I don’t know of any existing tools to do that.