How deep do you need to know the BEM methodology?

Question

BEM

There are principles of BEM class names, BEM nesting, BEM styling of CSS, it's all understandable. But when reading the documentation, it is not limited to this only, there are sections about: platforms, file structure, templates, DEPS specifications, etc.
Is it enough to know BEM for css and BEM for html to maintain a large site with repetitive components, or do you need to read all the documentation?

Answer 1

The hero was expected and he came unexpectedly.
You need to know enough BEM to grasp the concept and deal with controversial issues. I have collected a lot of material here under the expansion of examples and clarifications.