C Programming - Strings

Which of the following statements are correct about the program below?

#include<stdio.h>

int main()
{
    char str[20], *s;
    printf("Enter a string\n");
    scanf("%s", str);
    s=str;
    while(*s != '\0')
    {
        if(*s >= 97 && *s <= 122)
            *s = *s-32;
        s++;
    }
    printf("%s",str);
    return 0;
}

Which of the following statements are correct about the below declarations?
char *p = "Sanjay";
char a[] = "Sanjay";

1:	There is no difference in the declarations and both serve the same purpose.
2:	p is a non-const pointer pointing to a non-const string, whereas a is a const pointer pointing to a non-const pointer.
3:	The pointer p can be modified to point to another string, whereas the individual characters within array a can be changed.
4:	In both cases the '\0' will be added at the end of the string "Sanjay".

Which of the following statements are correct ?

1:	A string is a collection of characters terminated by '\0'.
2:	The format specifier %s is used to print a string.
3:	The length of the string can be obtained by strlen().
4:	The pointer CANNOT work on string.

Which of the following statement is correct?