Afaik, the dupe was possible but Ive read somewhere that Kakao changed the internal workings of the game. This includes the new packet encryption. The changes was applied probably after Kakao obtained the rights to stop Pyx Bot.
As for Lag Switch, its possible but Im not too knowledgeable in this field.
Afaik, lag switches works 50% at most when at FPS games but I havent heard much about it on MMORPGS.
But usually, when it lags in your end you'll just appear standing in 1 point from the view of other players.
On client editing/memory editing, its possible to do a 1 hit hack in most MMORPG.
Here's a sample of someone 1 hit hacking on a game.
Edit:
There's also a way to do 1 hit hacking using Packet manipulation.
Look for MuPie a very very old 1 hit hacking packet tool I used to use almost 15yrs ago. lmao