Is Recovery Mode necessary to flash to newer Android version manually? My phone (Sony Xperia Go) seems to be not able to boot into Recovery Mode

Is there some alternative way or tool to use for flashing ROM? (to latest kitkat mod). To avoid recovery mode

I have fastboot working on computer
Note: Installing the custom recovery using the tools below requires a rooted Xperia Go. Generally root isn't always necessary and a device can be rooted by flashing a pre-rooted ROM for example, and a recovery flashed via fastboot as another example. Also note it can brick your device. I take no responsibility for the below if your device turns into a shiny paper weight

The below is for a Windows Machine only:

To install a custom recovery, clockworkmod-recovery in this case: 


Place the archive you just downloaded to your Desktop.
Extract files from the archive to your Desktop.
Turn ON the USB debugging function on your device by going to Menu&gt;&gt;Settings&gt;&gt;Developer options&gt;&gt;USB debugging.
Connect the device to your PC using the USB cable.
Double-click on the install.bat file and the utility should launch.
Follow the instructions displayed on your screen.
Once Recovery’s installed, reboot the device.
You’re all set!