when creating the access rule, the value is what shows the php code.
the Compare to shows the entered number 1.
For the value, you click the lightning bolt and select the dynamic checkout querystring variable. this creates the php code in the value box.
you set the compare to box to the static value "1".
In step 2 of the tutorial you add the page access rule to the checkout page, so that the checkout page will only be accessible if you are logged in.
That is correct the checkout page will not show the cart contents, it should not.
The cart contents will be shown on the confirm page, you should not be storing the cart in the database on the checkout page.
if you used the checkout wizard to create the checkout pages, it will set up the functions to store cart information for you.