Hi @Monica, thanks for your post! I hope I’ve been able to address your questions below, however please shout if I’ve missed anything.
Disabled buttons
These are inactive UI elements that are also not focusable. We will be updating our guidance to advise, where possible, only use where research shows it makes the experience easier for users as they do have low contrast and can confuse users.
Footer
Yes the “Built by the Digital Design System” is example text and can be removed. You are also able to use a larger typography style where desired.
Radio buttons
We looked at the issue with focus on radio buttons. The problem is with this particular example and not component itself. As we have multiple radio boxes on the page and they share a name only first one gets a focus. We are working to fix the example in next few days but you can safely use the component itself as it’s working as expected.
Thank you again for your questions and feedback, we really appreciate it!