Undo all those changes, the second is actually dangerous and majorly insecure.
Try this address:
http://127.0.0.1/phpmyadmin
If that works then you have a IPV4 , IPV6 issue and you should do the following:
check c:\windows\system32\drivers\etc\hosts
It should have
127.0.0.1 localhost
in it and not
::1
Then edit httpd.conf ... use the wampmanager -> Apache -> httpd.conf link to ensure you edit the correct file.
Look for the line
Listen 80
and change it to
Listen 0.0.0.0:80
This will make APache only listen on the IPV4 network. This is so that the security for phpMyAdmin will work properly as that only allows 127.0.0.1 to access the phpmyadmin app. You may well be getting there on the IPV6 network which is ::1 and therefore fails the security check.
It may sound complex but its there to protect those who dont know enough to make there systems secure.