Vishal Shetty

Before you start learning React.js, make sure you know at least the basics of Javascript.
As React JS is front end library, you will have to study CSS as well, but if you are new to CSS stuff, then that won't cause any issues for learning React JS.
You can learn CSS anytime, but planning to start learning React JS then learn the basics of JavaScript and know the difference between Synchronous & Asynchronous Programming.

Don't get confused with Node.js and TypeScript, they both are different.

Node.js is a JS framework which runs on the server side and uses Javascript or Typescript.

Whereas Typescript is a superset of Javascript, that means TypeScript is written on top of the Javascript by Microsoft. 

So you can either use Javascript or Typescript for writing the code, this is applicable to Node.js as well.

You can say that few of the JavaScript issues are addressed by Microsoft and they were rectified in TypeScript.

Example, In javascript variable declaration, is done like this

var a = 10;

Here, we aren't specifying the type of variable a, if 10 is assigned then Javascript considers it as a type Number and if a string is assigned then Javascript considers it as a type String.

As humans tend to make mistakes, there might be a possibility that somewhere we assign a variable 'a' the string value or any other type value,

say a = 'string' or a = true;

So in Javascript, we are not binding the variable to any type, such issues were addressed by Microsoft and using TypeScript you avoid such issues.

In typescript, 

a:number = 10;

If by mistake, we assign variable 'a' value of type string or any type, It will throw an error message.

a = 'string' or a = true, it will not be allowed using TypeScript but is allowed in Javascript.

So, Learn Javascript, then learn Typescript then go for Node.js.

And yes learning Node JS is worth give it a try. 

I am working on React JS and Angular JS as well. I am a beginner in Angular JS but I have 2 years of experience in React JS. Trust me learning React JS was much much much easier as compared to Angular JS. Both of them have there own pros and cons, but why learning React is easy? Because React JS is just a library and Facebook has kept the flow and everything simpler in it, whereas Angular JS is a complete framework where you don't have to depend on many external libraries which makes it a bit hard to learn as compared to React JS. The change detection functionality of React JS is much better than what Angular JS is having. 

None of them are bad for SEO, the SEO problem with single page applications is that when Google web crawler comes for indexing your web application build with React/Angular/Vue it finds there no HTML tags and data. Everything in React/Angular is Javascript and crawlers only understands HTML content. So crawlers find that these web applications have no HTML content or it is blank, then it will not index your web pages and hence your sites won't be found in the search engines. To tackle this problem there are many packages available which generate the actual HTML which crawlers can index. There is the concept of server-side rendering which solves this issue. In both React and Angular, you can use server-side rendering and your web pages will be crawled and indexed by the crawlers. Read this article https://angular.io/guide/universal#why-use-server-side-rendering

First question, why you want to learn both React and Angular at the same time?

The purpose they both serve is same, so you should concentrate on anyone and then you can learn another one.

Even if both serve the same purpose, the flow of both is a bit different, If you start learning both at the same time you will be more confused and you will end up learning none.

I learned React JS first and worked on it for at least a 1 year and got hands-on it, then I started learning Angular and now getting hands-on on it. 

It was very easy for me to learn the Angular JS as I was already familiar with React JS and the terminologies and building blocks of the React library.

So start learning one, do at least a single medium scaled project and then proceed further learning another one.