Real 1
You are on the right page but you are probably working with the wrong injection.
Take a look at the php manual here
Well, you're trying to use a javascript injection to change a value that resides in a locally stored cookie, it would be a lot easier, and make more sense, to just simply edit the cookie manually.
This eliminates the right/wrong page issue and any errors in the syntax of your javascript injection. Remember that some of those articles are 10 years old or more, and as such may not always contain the more logical and modern approaches that we all take for granted today.
I feel like this challenge was a little weird, I changed the A****D multiple times but not on the right page and it didn't work unless I was on the correct page, also, I even cracked the admins password hash and I was unable to login. It would be cool if the creators would actually add the admins account to the database.