Answer 1

Hi! there is no reasons you shouldn’t learn React.js as well as others js based frameworks but if you’re new to javascript and web dev, it will be overkill to start off learning a framework
The best way to start is to learning Vanilla JS and once you feel confortable with it then, you can start learning react.
i have not personnally learned any js framework but i know react can be use to build natives mobile apps as well as speed up your web dev process. It’s always a good thing to understand what’s going on under the wood.