Choosing a platform for the project. How flexible is Bitrix and how is it stronger than Drupal?

Question

Drupal

There is a project, an organization's website with a very rich and non-standard future functionality. In particular, the portal needs a chat, a news module, a service order form, and all this is rather non-standard, with its own features, and it also needs its own API for the company's partners, the integration of their sites with ours will be quite deep.
There will also be a store on the site in which you need to make the function of placing goods in a general store - such as Amazon within the same industry and region.
More than half of the things have to be developed independently. Hence a number of questions:
1. How flexible is bitrix when it comes to developing its own functionality?
2. Will it be possible to update a heavily cut bitrix without problems?
3. Which CMS will have the fastest development speed if we have a team of experienced developers who, at the same time, had no experience with either engine or the other?
4. How easy is it to integrate support for payment systems popular in Russia into Drupal Commerce?
5. Bitrix seems to be the only system so far in which the issue with FZ-54 has been resolved. How easy will it be to solve this using Drupal?

Answer 1

Drupal is much better in terms of code. More flexible, more scalable, you can do CI. In Bitrix, the deployment issue between the dev->stage->working server is not resolved for the team at all, in Drupal8 it is now out of the box (thanks to the configurations).
According to 54-fz, everyone is doing it under Drupal already, https://www.ra-don.ru/shop for example. There are plenty of integrations with payment systems (and it’s also much easier to write new ones than for Bitrix!)