The fact that we provide state funded police protection to a very rich family is all to do with the Queen (or whoever is our monarch at any particular time) being our Head of State. I would like to live in a true democracy and have an elected Head of State, but that’s not how it is. We have to work with the status quo, and so at this point in time, certain royals get full time police protection, and other royals get temporary police protection when engaged in royal duties.
Obviously our Prime Minister gets full time police protection, and I believe all ex Prime Ministers continue to receive protection for the rest of their lives. I don’t know about any other government ministers, I suspect not, but I don’t know.
With regard to Harry becoming a regent if Charles and William died, I believe that is correct as nothing has been changed since Harry abdicated his royal duties and status. Anyway nothing has been changed as far as I am aware, perhaps others know more. I’m not sure that the public would find this acceptable and it could cause more calls for an elected Head of State. I don’t know, I hope it never happens. It’s very unlikely.