1. Given a string, reverse the order of characters.

2. Given an array of integers, return a new array where each element at index i of the new array is the product of all the numbers in the original array except the one at i. This should be done without using division.

3. Write a function to count the duplicate elements in a string and sort them in ascending order.

4. What is the difference between the find method and the aggregation pipeline in MongoDB?