In this task, you are given inputs 'i', 'j', and A, where 'i' and 'j' are integers and A is a list. A list is shown by two brackets and comma-separated numbers and characters inside, like ['1', '12', 'l']. You need to concatenate all elements of A from the ith element to the jth element, and then reverse the resulting string. 'i' and 'j' will be non-negative, and will always have a value less than the length of A. 'i' will always be less than 'j'. Perform the operations in order, i.e., do not reverse first and then concatenate.
20, 21, ['9837', '6343', 'W', '6925', '6931', 'H', 'J', '225', '7229', 'v', 'W', 'J', 'K', 'J', '6409', 'U', 'b', '1509', '2733', 'Q', '391', '3203', 'V', '1011', '1179', 'H', '6725']