How Do I Re-activate My Square-enix Account

You can never change the name unless you have SE do it. At some point a few years ago, first and last names got switched on some(or all?) accounts due to a database error though. Try asking customer support to switch them.

Don't think you can see any of the registered info.

https://secure.square-enix.com/oauth/oa/oauthlogin?response_type=code&redirect_uri=https%3A%2F%2Fsecure.square-enix.com%2Faccount%2Fapp%2Fsvc%2Ftop%3Frequest%3Dpoltop&client_id=account_manage&facflg=1

The above link is where you would reactivate your account. If you don't have your SE I.D. and PW the above link wont do much for you. There is however a way to regain your information if you have access to the email you had used when starting the game. Go to the "Forgot your ID or password" link on the page. Type in the original email address and gain access to that email. Follow the link SE gives you to gain access to your account.