(Assuming between friends)
1. How old do I look? => 나 몇 살이나 돼 보여? / 나 얼마나 나이 들어 보여?
2. You look younger than your age. => (넌) 나이보다 어려 [젊어] 보여.
3. Do I look younger? => 나 더 어려 [젊어] 보여?
4. I'm your unni/noona. => 내가 너한테 언니야/누나야.
5. How old are you? => 너 몇 살이니?
* People in their 30s and up would like to look young, which is 젊어 보이다. Youths in their 20s are already young enough, so they might talk about looking younger than their age, which is 어려 보이다.