How do I target the 3rd entry and only that entry?
As soon as you apply .all(), the variable you're working with becomes an array. Which means that the .offset(2) needs to be applied before you convert it into an array.



UPDATE

As @andrew.welch points out in the comments, it's as easy as grabbing the third item in your array...

items[2]


Ultimately, it looks like you want something like this...

{% set cardC = items[2] %}

{% if cardC %}

    {# ... the rest of your code #}

{% endif %}




ORIGINAL ANSWER

Once it's an array, you'll need to use the Twig syntax instead...

items[2:1]


Which translates to: "get third item (0-based index), limit of one".