Editable fields during registration, read only in Profile page

Hi,

I would like to have a field where the user chooses its subscription plan during registration (Silver or Gold).
Later, when the user sees its profile, this choice should be read-only.
How can I do that?

Similarly, I would like the admin to fill in a field to specify whether the user has paid his yearly subscription. The user should be able to see it but not be able to change it. Is there a way to achieve that?

Thanks for your help