Solution as per link provided by OP:
Vijesh finally was able to solve his issue using the All-In-One Toolkit, following the instructions from this XDA thread. This toolkit requires Windows. Not explicitly mentioned in the XDA thread, but most likely this means you've also to install the appropriate device drivers for your smartphone. But it looks like the toolkit offers to do that for you as well, see the item I - Install APX drivers in below screenshot:
The All-In-One Toolkit (Source: XDA; click image for larger variant)
The tool seems to be pretty self-explaining. For the installation, you simply run the self-extractor, which prompts you for a target directory. Then you start the tool, and select the wanted item (here probably 6 - LG Update Tool). Again, everything runs almost automatically -- simply follow the instructions given. The
.kdz file should be flashed then to the device, and you'll end up with the fresh ROM installed.