Lineage Eternal: 2014 VS 2016 UI Comparison Indicates the Game Has Changed a Lot
If you take a look at the UI in 2014, you can see the game was about controlling one character to explore and fight.
Now take a look at the UI in 2016, you can see the game allows you to press F1, F2, F3, F4 to switch between 4 selected heroes.
I will update the Lineage Eternal CBT1 information on this page. If you are interested, check back regulary for new updates.