The library function used to find the last occurrence of a character in a string

The library function used to find the last occurrence of a character in a string is

2) What is the output of this C code?

#include <stdio.h>
     int main()
     {
         char *str = "hello, world\n";
         printf("%d", strlen(str));
       }

3) What is the output of this C code?

#include <stdio.h>
     int main()
     {
         char *str = "hello";
         char str1[5];
         strcpy(str, str1);
         printf("%s", str1);
     }

4) What will be the output of the following program?

void main()
 {
       char str1[] = "abcd";
       char str2[] = "abcd";
       if(str1==str2)
             printf("Equal");
       else
             printf("Unequal");
 }

5) What is the output of this C code?

#include <stdio.h>
     int main()
     {
         char str[11] = "hello";
         char *str1 = "world";
         strcat(str, str1);
         printf("%s %d", str, str[10]);
     }