Adding drop-down options to "cart button"

Hi all, I am enquiring how to add drop-down menus to Squarespace's "cart button" pleaseeee;

1. when cursor presses cart button, it drop-down and quick views what items had already been added.

2. would like a separate "View my Shopping Cart" button at the bottom of the drop-down item list - upon pressing, then it will guide me to the checkout cart page.

3. one item per category must be mandatory to be added into chart before you can officially check out - like a bundle package & fixed bundle price

(example found below)