Firebase Cloud Messaging on iOS not working properly

I added to my project Firebase Cloud Messaging for receiving and sending push notifications. I followed steps in original tutorial from Google. The result was exciting, I can receive push notification on my device - I published it to TestFlight - problem occurred.

I realize that I need to create different certificate. (???) Then I delete my key (.p8) from Firebase Cloud messaging and recreated it (development too) + I recreated same development provisioning profile (old ones I revoke), I repeated process from tutorial but now I can't get push notification even in my device, neither on TestFlight.

Can anyone help me with these questions?

1. Which certificate/profile I should create? For now, I have created .p8 key for development and provisioning profile for development (not working anymore)
2. Should I change something in my code? I found somewhere that I should change URL from sandbox to prod, Firebase do it automatically? It's problem in device token? I can't recieve even test notification when I copy / paste FCM token to console.
3. It's possible to send silent push notification from Firebase Messaging Console? (Can I set all required headers in Firebase console?)
4. Difference between .p8 and .p12? It's possible to have .p8 key for production?

Please help me from this. Thanks!

[UPDATE][SOLVED] After completing the steps from this answer and changing the Team ID in Firebase to same Team ID from Apple Developer I was able to receive notification to my device and all the TestFlight devices.

Firebase has nothing to do with the development and production. It would be on your end if you are using two different firebase apps, one for the development and other for the production.If that is the case you just have change the GoogleService-Info.plist for the respective environments. Here are my steps you should follow to properly implement Firesbase Push Notifications.

1) Go to your apple developer account and create a new key for APNS. (Reference)

2) Create a firebase project and add an iOS app, then in Cloud Messaging tab in the your App settings add the Key you just created in the 1st step with KeyID and TeamID.

3) Add the GoogleService-Info.plist to the root of your project and add the Push Notification from the capabilities in Xcode.

4) Then initialize the firebase in your app (Reference)

5) Add the code to ask for Notification permissions on app startup.

6) And finally get the fcmToken from this method

func messaging(_ messaging: Messaging, didReceiveRegistrationToken fcmToken: String)

And send a notification to that token from firesbase.

Note: For provisioning profiles, enable the automatic signing in Xcode and Xcode will do the signing process itself. Now we don't need create the provisioning profiles manaually.