Auto Add Promo Items

or search frequently asked questions:

Remove free items from shopping cart
Can a rule be applied based on what other items are in the cart?
Can I limit the number of free items per order?
Can I limit the number of free items per several orders?
Can I use a rule “Get Free X when Y is spent”?
Can I add more than one free product?
Can I give customers a few options of free products to choose from?
Can I include shipping cost to the free product?
Сan a customer pick the size or other attributes of a free product?
How to use “Auto Add Promo Items with Products” Action
How to use “Auto Add Promo Items for every $X spent” Action
How to use “Auto Add Promo Items for the Whole Cart” Action
How to use “Auto Add the same product” Action
When I add to cart the product that triggers adding a free promotional product, the error occurs.
An error ocurred with Sage Pay: 3021 : The Basket format is invalid