Hi g4jc
Welcome to the forum, you might want to have a look at the following FAQ which explains where everything is.
Welcome to Benefits and Work .
You are correct, if you had to make a new claim then you would have to apply for AA as you are over SP age.
When you applied for a change of circs in September 2020, was this because your condition got worse?
If you reported a change then you would have received a PIP2 form to complete, this was the form that you filled in when you originally applied for PIP.
We do have some very good guides to help you, please make use of the latest version of our PIP Claim guide, have a look at page 96.
www.benefitsandwork.co.uk/help-for-claimants/pip Gary