EDIT: Check my Fake/Refurbished LG G3 thread for more easier instructions.
Its quite simple and does not require any laptop or anything else!
Note down the IMEI by *#06#, then follow these steps..
1.Make sure the cell is off.
2.Hold Vol up + Vol down + Power at the Same time and keep on holding until you see a White screen with "Hardware Control Written Over it"...
3.You can see the ORIGINAL IMEI at the bottom right above the bar code..
Confirm Model: [Updated] [RECOMMENDED]
Works Fine on Stock KK ROM with Stock Recovery, Doesn't Work with LP and JB
Else you can always confirm the Model if that is what you desire...
Things you need BEFORE buying..
Laptop with latest IOroot.zip [Check here] [You can also just download adb files from internet]
1.Download and extract the latest IOroot.zip
2.Enable USB Debugging. VZW users must also enable ethernet mode.
3.Now Change USB connection to MTP.
4.Open terminal/command prompt. windows/linux users: cd into /ioroot folder. mac users cd into /ioroot/mac
(windows users can hold shift key, right click in ioroot folder. Select "open command window" option.
5.copy/paste commands below
6.Now, you'll get "Authorize this PC", check always box[or whatever] and hit accept.
copy/paste commands below.. hitting enter/return after each line.
adb reboot recovery
[If you get device not found error, make sure you are following the steps else try disconnecting and reconnecting the USB cable]
Now at top of the recovery screen, you have your REAL Model
[Do not forget to say Thanks, if this saved you from a Scam! ]
PS: The reason i mentioned IOroot.zip is only that you can also root your device with it if you're on Kitkat