How can I change my blog's subdomain?

My blog is at theonlyrealtodd.hashnode.dev . I've given my blog the title "hacklemore" and thus having it at that subdomain is a bit awkward. Is there a way for me to move it to hacklemore.hashnode.dev?

If not, is there any other workaround?

I also have one other question: When I signed up, I used the GitHub login, but this username is actually not the handle that I use anywhere - is it possible to refactor my username in general?