This is how Fiverr works - people come here, order things and expect to get them.
I know many sellers here put all over their profiles to contact them first, but, buyers are NOT held to that. You cannot make someone message you first.
This part makes no sense in English anyways. What do you mean you are trying to “identify this buyer’s name?” We do not have access to someone’s account or real name here, and for good reason. There are a lot of nutty sellers who would go find someone on social media and harass them or worse. YES! I have seen it done over the years!
Why would you deliver work now after they asked you to cancel the order. You even stated:
which to me seems as though what they wanted you to do, cannot be done by you in whatever time frame the buyer expects.
YES, if you deliver something just to deliver, the buyer can give any sort of rating they like. If they want to give a 1* they can, you have no control over ratings that buyers give.
I am not sure why you think this is a fake buyer just because they just signed up in May of 2021. I have quite a few new to the site buyers who turn out to be great. Everyone is new at some point.
Maybe I just don’t get the gist of your story here.