What are the features when writing your own payment module for Bitrix (Bitrix)?

Question

1C-Bitrix

Colleagues, hello everyone.

I am writing a technical specification for writing my own Bitrix module for our payment system. I want to understand the issue.
In general, I have more or less understood, in general, this is a kind of php module that transfers the data on the basket to our payment system, if the payment is successful, the payment order is tapped back to Bitrix.

There are a couple of questions:
1) I look at other payment modules and see that there is such a checkbox "Allow to print a receipt", in this case, if the IM has an online cash register connected, then a receipt will be printed. There is a question - if we give such an option on our payment module "Allow receipt printing", then we should additionally tap something into Bitrix (i.e., the payment card should return something additionally) and if so, what ?

2) Where can I read the documentation in general on what parameters are required when creating a payment module, what parameters are optional? And maybe you can still somehow customize the payment module so that the manager, choosing certain parameters in the Bitrix admin panel, changes the logic of our payment page. Well, for example, is it possible to somehow set valid payment methods on the payment page via Bitrix, if the API of our payment system allows this?