People who are having LG G2 can install the LG G3 firmware on their device. So if you are not planning to buy LG G3 but you have LG G2 then you can use almost all features of the G3 in G2. But this procedure may brick your phone, so please do it carefully & at your own risk.
Please also note that this procedure will erase all of the data on your device, which is why you should perform a full backup of everything. To be able to backup your data, you can use an app such as Helium App Sync and Backup. You can also use Google Backup.
Please also note that this procedure will erase all of the data on your device, which is why you should perform a full backup of everything. To be able to backup your data, you can use an app such as Helium App Sync and Backup. You can also use Google Backup.