How well do you need to know react?

Question

JavaScript

Is it enough "main concepts" in the official docs to boldly indicate knowledge of react in the skills, or is advanced also needed?
Also, how long did it take you for main and advanced?

Answer 1

You can specify anything and at any stage of the study, it's just that few people are interested, no one looks at the "tags", this is noise. Your ability to solve problems is important to the employer, and not at all that you read the documentation blocks.
Can you solve problems using React? So you know React.
The more complex problems you can solve, the better you know. Knowing only about main concepts - on any real project you will get lost and you won’t be able to do anything sensible.

Also, how long did it take you for main and advanced?

A few hours to read the documentation. And before that, do the same thing for 10 years, only without React.
There is nothing archaic there. But bringing it to the level of automatism, developing good practices and gaining some kind of expertise - these are months and years of constant practice.