Awwwwwwwwww thats so sweet cali ,
generally we use Tum, for same age ppl , younger ones , and AAP to strangers and elders ..
Tum Kaisi ho ?? is formal way of asking
Tu kaisi hai , ----btw friends (female)
Tu Kaisa Hai ----- Btw friends (male)
actually i had all friends who talk in hindi since my childhood , so i have good command over that lang , but other family members hindi is comedy ..... 😆