I made in this post a little firmware update tutorial. However if you don't have the knowledge to do this, ask for someone's help. I am not, in any way, responsible for any bricked devices.
So now, let's see the good news.
I just updated manually the firmware, cause OTA it was not available(although it apears on my country's website, but probably wasn't published on the update servers) and the first thing I've noticed is that the startup is even faster now. On previous version (4.01.00) upon turning on the TV and wanting to change the channel would take from 6-7 second up to 11-12. With 4.05.01, I can change the channel in 2-3 seconds. Also, the animations when moving through the menus seem to be a lot faster. Regarding if this is a lite version of webOS 3.0(e.g.: new menu icons, multiple user profiles, magic zoom, ), I think it is not, since I haven't noticed any new features compared to the old 4.01.00 version. I think this firmware brings only performance improvements. But we are on the right path.
So if anyone was wondering, in order to update the firmware from the USB memory stick, you need to follow next steps:
1. Connect USB Stick to PC or MAC and create a folder called "LG_DTV" on this USB stick
2. Download the update firmware from this link http://www.lg.com/uk/support/software-firmware. Insert your TV model and hit Search button. Download the latest version updated on the latest date(4.05.01 was published on 13.06.2016) and extract it on your desktop/download location. Now you will have a .epk file extension called "starfish-dvb-secured-m14tv-1.biscayne.m14tv-145-04.05.01-prodkey_usb_V3_SECURED".
3. Inside the LG_DTV folder copy the extracted file with .epk extension called "starfish-dvb-secured-m14tv-1.biscayne.m14tv-145-04.05.01-prodkey_usb_V3_SECURED" and then, safely remove the USB Stick from PC.
4. Connect the USB Stick to one of the TV's USB ports in the back and now SmartShare app will appear and also a notification to install the new Firmware.
5. Close the SmartShare app, and go to Install option. Now you have to wait...Read step 6
6. When the TV will have copied the Firmware from the USB stick, a message will appear on the upper right corner which will say that the new firmware will be installed upon rebooting the TV.
7. Shutdown the TV and hit the ON/OFF button on the remote again to turn it on, wait for the new firmware to be installed and configured. All your programs will remain in the order they were saved(so no need to configure again the channels) and also all the apps will be installed(no need to reinstall them).
That's it. Enjoy your new faster TV.