응 is yeah, 네 is yes.
응 is not formal.
If you say 응 to your boss or elder they might not like that all.
even 네 is not VERY formal. 예 is the way to say yes to your boss or grandparent
seems kinda passive aggressive and awkward
I tried "yeah, you're pretty" and got a wrong answer ...
Is "Yes, you are beautiful." wrong?
Beautiful is 아름답다, pretty is 예쁘다.