Central Board Of Secondary Education [CBSE] — Different questions different sets .

Respected authorities.
This was my first time for appearing for class 10 board, I want to know that the different sides of different sets of paper contains different question or not.
After searching a lot I came to know that the difference of questions in the set is very less only the sequencing has been changed.

But I am very sad to say that, when I observe the set 31/2/2 &31/2/3 I came to found about the difference of 15 questions and of 28 marks.
I felt that the questions in said to were very easy as compared to set three. Earlier I didn't believe in luck but in real efforts but this time...
It seems that more than efforts luck is required... Different question have different opportunities for the same students. Whereas in my opinion all student should have almost every question same but in different sequencing.
I request u to tell if this is relevant or not .
Plz compare the sets ..it's a very humble request to u

I request you to correct me that efforts are needed not luck ...