uhh by that picture I honestly think you can pass as about.. 14 years old boy

Your skin is really soft, your face is a bit "swollen" not exactly feminine, I am not sure how to explain it.
I think you could pass but as really young.
To make it look a bit older, you need to make the skin look rougher, like testosterone does.
Maybe tan? (especially at the face).
I know people used make up, not sure how, to make fake stubble.
There is also the fake ones that you kind of attach.
Hairline can do but sounds like such a hard work and personally, scary thing, but we come from other worlds I guess

Your hair is brown, mascara is usually black, (although comes in many colors), like people said, use eyeliner, not mascara, eyeliner can also draw around the eyebrows and inside, making density seem greater, mascara would just help to color what hairs you have and if they are white/transparent at the end, it makes them seem longer, even though they are not longer, just fully in color.
Perhaps eyeliner can be used to create stubble? It might look silly for you though.
Can I have your high soprano voice please?

O have hard time reaching the high notes for now

But I did see a young boy from that picture initially, how old are you?
Hope any tips helped..
Dennis - you? look like a girl? ha ha!....... HA!

That picture makes you look like a kinda serious forest ranger guy ^^ you're doing great!
Edit:
Forgot to say, testosterone does seem to work pretty much for anyone, it might just take more time for some.
I also know what you meant about perception, I had days I thought I look .. and was sometimes surprised!