Yes it is possible to power up the board by using VIN pin. Check the Intel® Galileo Gen 2 Board Schematic , on sheet 27 (Voltage regulators) you can see that VIN is connected to the U6 DC-DC converter, so you can power it up from 7V to 15V. But if you decide to use a battery, make sure the USB cable is not connected when the battery discharges. Powering up the board only with the USB cable can damage the board, so make sure the board is always powered through VIN or with the power supply when the USB cable is connected. About your second question, I suggest you to boot from an SD card image the one on this site or IoT image. Then make sure you have installed GCC, if you are not you can get it from here or for the IoT image in this repo. With GCC you can write your code in C from the Linux side of the board, compile it and create an executable, without the need of the USB cable to upload your code into your board. Take a look at this guide on how to use GCC. Let me know if this is what you are looking for.