Some things to check.
The 404, that is probably because your web server isn’t configured correctly.
If you put a simple page in your WP root, like foo.php
<?php
echo "You made it";
and if you go to
[my-domain-url]/foo.php
and you don’t get “you made it”, then your webserver is misconfigured OR your DNS isn’t pointing where you think it is pointing.
So as far as webserver configuration, if its apache, you have to map the DNS to the virtual host. My guess is that part is missing.