Rakesh Mittal, I'm not sure you're asking the question that you actually want an answer to. I suspect what you're really trying to ask is how much time is it going to take you to build a foundation strong enough that you can do research in these areas. Obviously a lot of that is going to depend on how much you are comfortable now, what other demands there are on your time, and how quickly you learn things.
Typically people start getting to the point where they can start doing mentored research about a year or so into their graduate studies. That's after having done a 4 year degree of full time study as an undergraduate. And even then, the research is very focussed in one area, and it requires a large degree of input from a supervisor who conducts independent research in the field.
Studying on your own, without mentorship is very difficult, because you don't have much by way of feedback to know if you're understanding things properly or not. That's not so say it's impossible, but if you're really serious about mastering physics to the point where you can do research in these areas, you should seriously consider graduate studies.