Answer 1

People usually use some libraries like p5.js or three.js to create animations and effects with Javascript. This might need more advanced skills, especially for 3d you need some basic math too.

https://p5js.org/
https://threejs.org/

If you want to do something similar, it makes sense to study other people's codes in detail, and observe how they do it. Try something very simple first, you need solid foundation before you can do more complicated stuff.