Hello, to revert to Jellybean you need to flash a KDZ file of Jellybean, here you can find it:
(Every with V10 version is Jellybean, V20 is KitKat)
After installer the Jellybean rom and finish with the flashing, you need to do a hard reset or it wont boot.
Press Volumen Down - Power Key and Quick memo Key at the same time
When LG logo appear, release the Power Key one
When LG logo disappear, release all the buttoms. It'll appear a Android robot and when it finish, boot.
If u don't know how to flash KDZ ask me!