Lets say A is the owner. I want B, C and D users from our team to be able to upload the new versions of our application. Is this possible? From this it is not very clear to me what kind of permission has a user. If somebody has any experience to this part is welcome.
You need the google account details to sign in to the Developer Console.
Any application uploaded to the play store must be signed.
Android requires that all apps be digitally signed with a certificate before they can be installed. Android uses this certificate to identify the author of an app, and the certificate does not need to be signed by a certificate authority. Android apps often use self-signed certificates. The app developer holds the certificate's private key.
Signed apk file have a binary file it build and signed with. Only the developer have this file on his own computer . Once an application first signed and was uploaded to the store all the other versions of the app must build and be signed against the same binary file. If a developer looses this file he will no longer be able to publish updates to his own app .
Warning: Keep your keystore and private key in a safe and secure place, and ensure that you have secure backups of them. If you publish an app to Google Play and then lose the key with which you signed your app, you will not be able to publish any updates to your app, since you must always sign all versions of your app with the same key.
(from the same link)
It is possible to add another user permission to your Developer console.
Here list of permissions you can choose to share:
These permissions can be Global to all apps on account or only for particular apps. Anyway if you share Manage Production APKs permission you'll have to share the signature file as well.