How to freelance develop an application in Unity for Google play?

Question

Unity

Accepted an order for the development of an application on Android (transfer the project to Unity). A problem started when testing user identification in Google play.
The bottom line is that, as I understand it, I will not be able to sign the application without using their .keystore.
In other words, I can't test-authorize in the game, because. I don't have this app on Google play (I don't have a Google Play Console account, nor the app I'm developing in it).
I correctly understood that it's better for me to create a separate account in the Google Play Console and play with it, and when they release, they will configure the keystore themselves?

Answer 1

No.
There are sections for development.
Do everything at once on their account.