Re: 404 on all admin files
... and now you have told the whole world the "secret" - you need to name the admin something that is not guessed easily and NOT tell what it is. (and you'd be better off to delete the installation folder completely - it is not needed for anything after the install)
Perhaps reading the recommendations in the /docs folder regarding security would be good too.
Please do not PM for support issues: a private solution doesn't benefit the community.
Be careful with unsolicited advice via email or PM - Make sure the person you are talking to is a reliable source.