Replace Apple In-App purchase with custom bitcoin based prefill system

Apple thoroughly documents the requirements for participating in their stores at the developer website:

https://developer.apple.com/resources/

You should review the iBooks and In-App Purchase from the above page.

At that point, you should be ready to read and digest the actual App Store Resources themselves to figure out what sort of effort you'll need to expend to sell your content through Apple.

https://developer.apple.com/appstore/index.html

Assuming you are on iOS - you can skip the parts on the Mac App Store. The review guidelines have some of the information you'll need.

No, Apple Pay is for physical goods or services only.

Apple Pay or In-App Purchase

It is important to understand the difference between Apple Pay and In-App Purchase. Use Apple Pay to sell physical goods such as groceries, clothing, and appliances. Also use Apple Pay for services such as club memberships, hotel reservations, and tickets for events. On the other hand, use In-App Purchase to sell virtual goods such as premium content for your app, and subscriptions for digital content.

^{Source: https://developer.apple.com/apple-pay/Getting-Started-with-Apple-Pay.pdf (page 2)}