don't worry yoghurt_girl85
I am also 22 like you, also asian.
I get a lot of "you look like you're in high school" bc of my baby face too.
But it really depends on what you wear and what you make yourself look like.
When I went to the open day, I put on my dress skirt (they like pencil skirts that are fitted but not too fitted), and a shirt and a conservative blazer jacket. I even bought a red lipstick that I had never worn in my life, put my hair in a neat bun. (I would have never gone anywhere else looking like that.)
I think the right appearance is very important for EK. You have to look classic and conservative.
I really think the red lipstick worked out for me. Nobody would say I look 16 when I have my red lipstick on.
You can make yourself look older, not too old. Just the right age for to be a cabin crew.
Good luck!