What license should I buy to use an item on a book cover?

After selecting the appropriate cover design from graphicriver and redesigning it (changing photos, inscriptions, layouts) for the customer who will be selling the book what license should I choose?

Extended. If the end user (i.e. the people who buy the book) are charged to view/access the item, then you need an extended license.

Approx. So if I want the customer to present 2 different projects then I have to buy 2 standard licenses and when the customer selects the model and will sell the book eg bookstore, I buy for this project 1 extended license?

Easier to buy an extended license originally, rather than buying a regular license and then an extended license as well. And if there are two different projects where the end users are charged, then you’d need two different extended licenses.

But it sounds like you might be saying that… you want to make two different options for the client to choose from, with only one of those being the one that the client will sell? Then yes, two regular licenses to make the designs for approval, and then just one extended license for the design that the client chooses to use/sell… would be fine.

Ok, the above is clear. And what in the case of a promotional leaflet where I have purchased a standard license, I made a client a project for which I paid money but in addition to the print files wants to edit the project files. Can I pass it on to him?