Admin Login Error while working on Multisite

I was trying a create a multisite for Tanamera.
So, I followed the documentation Create a Network.
It was until Step 3, Installing Network that I started notice things were different, I was not able to choose sub-domain and sub-directories, I was only able to change the Site Title and Super Admin Email. (The multisite domain was directed to http://www.tanamera.com.my which I cant modify)
So I did change the super admin email, as it was the previous developer’s.
Then I copied the codes as shown on the next page to wp-config.php & .htaccess
I was not able to login.
And the site is down.
So I reverted both the files, the site seems to be fine, but I cant login with my admin account. (Wrong user or password is displayed)
And I’ve tried changing the password from phpMyAdmin, it doesnt work either.
Can anyone help me with this? Thank you!

P.S. I deactivated all the plugins, so most things doesnt work on the site, and it needs to be up and running again within hours.