Okay this is like another language to me since I have no idea how to make this into TWRP flashable package I just restored my nandroidthe /System that you found there is TWRP's system folder, not the system folder or the ROM. you must have a TWRP flashable package containing the script to copy the build.prop in the MOUNTED system ROM's folder.Once done will copy your build.prop file.
Thank you for the help. Really appreciated.