Unlocking via Sony's Official website
Sony has provided a website where we get an unlock code for each IMEI no. type in that code and your bootloader will get unlocked officially . This is the easiest unlocking method possible . Wait there's more , official unlocking method does more bad than good , like
1. will void warranty
2. Will loose DRM & track Id related stuff
3. No official phone updates via SEUS/PCC or OTA
If you don't care about them please go ahead and click this LINK and follow on-screen instructions on that site
RELOCK : TO relock use this LINK
There is an alternative way to avoid the above mentioned limitations , it is called SEtool
Unofficial Unlocking (S1tool)
This method overcomes all the three limitations , but you will need to do a little work manually , this method introduces us to a new word called TESTPOINT(Of all those 8 golden points , only the point which is indicated by the arrow is the TESTPOINT) .For NEO V testpoint is located deep within a slot covered by a black patch which is above our SIMCARD slot (see this picture and remove the black covering) .