Is it profitable to specialize in the development of applications for the Bitrix Marketplace?

Question

1C-Bitrix

Over many years of experience in developing corporate websites and landing pages, my small web studio has accumulated a lot of interesting and convenient UI solutions for Joomla, Wordpress and just on the frontend without CMS.
There is a tendency for the team to engage in "endless improvement" of solutions already made and submitted. There are also developments of intelligent interfaces for tourism and construction companies. The main desire is to make UI applications based on mat. models, specialized formulas, etc. (handy calculators, tools for choosing from alternatives, etc.)
I have never worked with 1C-Bitrix, so there are a lot of questions.
Questions:
1. Is it possible to profitably enter the Bitrix marketplace with various applications?
2. What applications will "go" on the marketplace: templates, modules, complex thematic solutions?
3. How often do they need to be updated? In other words, how often is the Bitrix API for application development updated?
4. Is it possible to use an entire JS+CSS application that loads the main logic from a third-party server? Are there many of these on the marketplace?
5. For comparison, in your opinion, is there an acceptable market for sales of applications for Joomla, Wordpress and Drupal (paid applications, of particular interest to Russia + CIS)?