no dev mode is a sandbox VM for the xbox one, you do not have access to full system resources, in a way like java is a sandbox vm for effectively C/C++ code, although java does things like garbage collection for you automatically.
in dev mode you do not have access to the same filesystem nor any retail software, if I recall right you cannot even connect to and use xbox live
you have something like one cpu core and a small amount of ram and some gpu access, enough for homebrew things or emulators, not for running native assembler or C++ code to run custom kernels and run iso rips