Question 01:

Is there any technique where generating random number within a range is equiprobable ?

Question 02:

What is the extra advantage of the following method 02 and method 03 ?

srand(time(NULL);

//Method 01: general approach

int myrand(int mod){
  return rand()%mod;
}

//Method 02: Taken form red coder submission.

int myrand(int mod) {
    int t = rand() % mod;
    t = (1LL*t*RAND_MAX + rand()) % mod;
    return t;
}

//Method 03: Also Taken from red coder submission.

int myrand(int mod) {
	return (int) ( (((double) rand() / RAND_MAX) * (mod) ));
}