@alishanvr Let's tackle this:

In a computed property, you can access inner properties of it. Like, for example, suppose that the computed property someComputedProp returns an array. Then, later in your code, you can do someComputedProp.length and it will work. A method would not permit you to do that.
I don't know. I think btw that every prop you define inside of data will be reactive since this is the nature of Vue. The thing will be how to make it not reactive, but I am learning just as the others, so I can't answer this with exactitude.
Use this whenever you are accessing something defined inside data, computed or methods.

I hope my answers benefit someone doing this course today :)

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