1. How to quickly add SHA1 fingerprint to Firebase?

You can generate SHA1-SHA256 by using this command

keytool -list -v -keystore ~/.android/debug.keystore -alias androiddebugkey -storepass android -keypass android

after that add the generated key to your firebase.

2. How to test Google Play Billing 8.0.0?

1. Use Internal Testing (not sideloading)

• In Play Console → Monetize → Products, mark items as Active.
• Only Play Store testing shows test cards.

2. Add License Testers

• Play Console → Settings → License Testing → add tester Gmail(s).
• Also add them to your Internal Testing track.

3. Upload a Release Build

• Build and upload AAB:

flutter build appbundle

• Publish to Internal Test track.

4. Install via Play Store Link

• Testers install from the testing link (not adb).
• Purchases now show test cards.

5. Handle Purchases in Flutter

Use in_app_purchase plugin; listen to purchaseStream and complete purchases properly:

in_app_purchase: ^3.2.3

// 1. Listen early in initState
_subscription = InAppPurchase.instance.purchaseStream.listen(_onPurchaseUpdated);

// 2. Handle updates
void _onPurchaseUpdated(List<PurchaseDetails> purchases) {
  for (var purchase in purchases) {
    if (purchase.status == PurchaseStatus.purchased ||
        purchase.status == PurchaseStatus.restored) {
      final valid = await verifyPurchase(purchase);
      if (valid) {
        deliverProduct(purchase);
      }
    }
    if (purchase.pendingCompletePurchase) {
      await InAppPurchase.instance.completePurchase(purchase);
    }
  }
}

You can also follow this youtube video for your reference:

https://www.youtube.com/watch?v=u5p1P0gCmJo

3. Can I go to production in 36 hours?

• Coding/testing: feasibly yes if you freeze scope now.
• Review time (production): typically a few hours to 1–2 days, but not guaranteed.

Plan:

• Immediately push to Internal testing (instant).
• Validate Billing + critical flows.
• Then submit to Production with a staged rollout (e.g., 5%) to reduce risk.

4. Can I submit to store without login system?

• Yes — you can submit without login. Just add a guest mode so users can still use the app and make purchases without signing in. As long as login isn’t required to access purchases or core features, Google Play will approve it.