Unity Game Pre-Launch Technical Checklist

I am planning to launch my Unity game soon. It is a 2D word game.

I was wondering if there is any Technical Pre-launch checklist of tasks.

I have 2 questions:

1. Apart from below 2 points, is there is anything I should implement in Unity in 1st launch (which CANNOT be pushed in App Updates..)

2. Is it needed to do Serialization and Deserialization of Game Data? Is it helpful?

Recently, I faced some issues:

1. Unsigned APK: I forgot to sign APK. I used Unsigned (Debug) option to build APK and uploaded in Play Store. Later, I realized that I should Sign APK with Alias and Key and upload new APK with new Bundle ID.

2. Serialization and Deserialization of Game Data for Security: I am currently using PlayerPrefs to save data. However, I was told this is not safe and hackers can hack game data like Available Coins or any other variable. I was suggested to do Serialization and Deserialization of game data and do Obfuscation on top of it. Itseems that this should implemented in 1st launch only. If I do this in update, the player progress will be lost itseems. But, another dev suggested that no matter what we do, hackers will find a way to hack. Even Candy Crush was hacked itseems. And my dev says, it is possible to add security features in future updates also. So, I am confused.

Please help..