I was wondering if its applicable to open android app which is already installed in phone inside unity scene like firefox or Twitter.
You can not open a instaled app inside unity but you can open a web frame check this repository
I like that question. If it doesn’t have to be IN the game, you could create a link which opens the app on the phone.
I can’t tell you how, but I’ve seen it in leader boards from different games, where you can post your score on social media.