You can definitely delete your app! The command is fly apps destroy. So it sounds like you’d want to re-create your apps with a different name.
A few commands that might come in handy here:
You can list all apps with fly apps list;
view their configs with fly config display -a $app-name,
and check what image you’re using with fly images show -a $app-name.
If you haven’t already, it’s definitely worth enabling fly completion for your shell-- this makes exploring our docstrings for flyctl subcommands a lot easier!