It's really not clear what you are trying to find out.
Things I can say:
How to check if record already exists when UPDATING? -> you can't update something that doesn't exist.
If the issue is that you don't want record 1 and 2 to have the same value in a certain column you could set the field in MySQL to unique value.
In your PHP code you seem to check twice if a user already exists:
echo 'User already exists';
/* check user already exists or not */
$temp=mysql_query("SELECT 1 FROM admin_login WHERE email = '$email' AND id != '$id'");