Register as a public developer for Amazon SP-API?

I am trying to register as a public developer for Amazon SP-API. I have seller central account of my client. Later, I also want to publish my application and services in the selling partner appstore of Amazon.

But as per the SP-API Documentation, I need to have a seller central account to register as a public developer. I work in a data analytics company which is trying to build integrations for Amazon Seller Central and Vendor Central Platforms using SP-API. If I use my client's seller central account to register as a public developer then will my developer account will always be connected to that seller central account (which does not belong to our company in the first place)?

And we can only publish applications using that seller central account?

Goal: Register as a public developer to get access to SP-API. Publish apps in selling partner appstore where clients with seller central accounts can authorize us and use our services like other applications registered in the appstore.

Yes, if you create a developer account with your client's seller central account it will be associated with the client account. As far as I know, you cannot transfer the ownership.

I would recommend creating your company's seller central account. It's a simple process to register as a seller. You will require a few tax-related documents and government IDs that's all. Check out here for more info.

Once you have a seller account you can create a developer account from here. The next step would be registering your app and then publishing it on the Amazon app center. Check out the below link for details on how to list your app on the app center.

https://developer-docs.amazon.com/amazon-business/docs/app-center-listing-process