Is it possible to know only JavaScript, CSS and HTML to work as a programmer?

Answer 1

working as programmer means learning and being able to understand each language so you can understand a program 90%.
you should have knowledge about concepts

Answer 2

Unlikely but not impossible. Look at job adverts. Back in the early 2000s you could get away with knowing one programming language, or have a narrow amount of knowledge, these days employers want a lot more.

Answer 3

very hard but possible... you can code for mobile(android).. using webview

Answer 4

Вика только верстальщиком или веб-дизайнером.