So it is possible to...

Thank you for all the valuable info given.

After reading, I just have 1 more question. If I somehow know the packet that my client sent to connect to the game world, can I send that packet without logging in, and be able to load mabi world directly without authentication?

In theory, yes. In practice, it would be horribly complicated. I haven't played around with the idea, but you'd need some illegal tools, and even then it probably wouldn't work, if Nexon uses even basic security.