Как выполнять проверку OTP каждый раз в базе данных Firebase Realtime?

Этот метод может отправить OTP на ваш номер Mo.

    PhoneAuthProvider.getInstance().verifyPhoneNumber(
    phoneNumber,        // Phone number to verify
    60,                 // Timeout duration
    TimeUnit.SECONDS,   // Unit of timeout
    this,               // Activity (for callback binding)
    mCallbacks);  

Вам требуется перезвонить, чтобы получить ответ

    mCallbacks = new PhoneAuthProvider.OnVerificationStateChangedCallbacks() {

@Override
public void onVerificationCompleted(PhoneAuthCredential credential) {
    // This callback will be invoked in two situations:
    // 1 - Instant verification. In some cases the phone number can be instantly
    //     verified without needing to send or enter a verification code.
    // 2 - Auto-retrieval. On some devices Google Play services can automatically
    //     detect the incoming verification SMS and perform verification without
    //     user action.
    Log.d(TAG, "onVerificationCompleted:" + credential);

    signInWithPhoneAuthCredential(credential);
}

@Override
public void onVerificationFailed(FirebaseException e) {
    // This callback is invoked in an invalid request for verification is made,
    // for instance if the the phone number format is not valid.
    Log.w(TAG, "onVerificationFailed", e);

    if (e instanceof FirebaseAuthInvalidCredentialsException) {
        // Invalid request
        // ...
    } else if (e instanceof FirebaseTooManyRequestsException) {
        // The SMS quota for the project has been exceeded
        // ...
    }

    // Show a message and update the UI
    // ...
}

@Override
public void onCodeSent(String verificationId,
                       PhoneAuthProvider.ForceResendingToken token) {
    // The SMS verification code has been sent to the provided phone number, we
    // now need to ask the user to enter the code and then construct a credential
    // by combining the code with a verification ID.
    Log.d(TAG, "onCodeSent:" + verificationId);

    // Save verification ID and resending token so we can use them later
    mVerificationId = verificationId;
    mResendToken = token;

    // ...
}};

И для проверки вызова OTP ниже метод

 PhoneAuthCredential credential = PhoneAuthProvider.getCredential(verificationId, code);


 private void signInWithPhoneAuthCredential(PhoneAuthCredential credential) {
mAuth.signInWithCredential(credential)
        .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
            @Override
            public void onComplete(@NonNull Task<AuthResult> task) {
                if (task.isSuccessful()) {
                    // Sign in success, update UI with the signed-in user's information
                    Log.d(TAG, "signInWithCredential:success");

                    FirebaseUser user = task.getResult().getUser();
                    // ...
                } else {
                    // Sign in failed, display a message and update the UI
                    Log.w(TAG, "signInWithCredential:failure", task.getException());
                    if (task.getException() instanceof FirebaseAuthInvalidCredentialsException) {
                        // The verification code entered was invalid
                    }
                }
            }
        });}