1.What is the basis of grouping of shares in different groups for ex. A group etc..

Since you've numbered it, I'll assume this was a homework problem. If that's the case, we aren't here to just answer homework questions for you. You should post your own attempt at answering the question first and let someone tell you if you're on the right track.

You also might clarify a bit more. I'm assuming you mean shares of stock?