how do i run an apk file on a web browser to make the apk know that it is running on a real device and not an emulator

I think if you use firebase-auth:20.0.0 or later (launched 2 days ago), or the Firebase BoM 26.0.0 or later then you should be able to use the reCAPTCHA flow of Android Phone Auth, which will work on emulators. Give that a shot and let me know how it goes 🙂