How to set up payment and download of a unique product on Wordpress?

Question

Qiwi

Good day. There was a need that I can’t resolve on my own, and therefore, I ask for help from those who understand how to create online stores on CMS Wordpress.
The bottom line is this: On the Wordpress site, you need to set up the download of goods after payment via Merchant WebMoney or Visa QIWI Wallet. At the same time, the product is unique (i.e., only for one user - for example, activation keys for programs or games). Consequently, one product is created, to which all the keys available to the seller are added, which are automatically deleted after payment and download by the buyer.
That is, the procedure is approximately the following: The buyer selects the product, pays for it, returns to the site, where he sees a link to download a text file with an "activation key". Once a file is downloaded, it is removed from the catalog to prevent another user from buying it.
In connection with the above, I ask for help on the following questions:
1) What plugins or codes should we use to make everything work?
2) Is it possible to set up all this without linking Robokassa (using exclusively the WebMoney and QIWI APIs?