How to get product variation of a single product in view Let's assume I have a product named A, B, C and each of those products have variations.

Now, when I am making a block in views, when I only have the option to select product variations as seen in this image: 



After this, there seems to be no way to select a product variation of say product A. 

All the variations are there by default.
You need to add a context to tell the view which product you want to show. Either from the URL with product id in url, or static product id number, or some other way.

The context filter for views relies on a url or some other way to set a value. In this case you want to select one of your products that has variations. So, if your url is /myproducts/1, the context filter can be set to use 1 for the product id and show only that product along with only its variations. 

How to pass Views contextual filter via URL?
https://i.stack.imgur.com/8cLtw.png

Use Provide default value from URL, then choose which part of the path will have the product id in it. Then when you link to this view, use the url that way.

On your index page view, you can make the links to products this way so it passes the product id to your page.