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.
18, 20, ['U', 'R', '5385', 'k', '4571', '3189', 'E', '9215', 'P', '2727', '3063', 'C', 'H', 'S', '2789', '5309', 'S', 'W', '7199', 'P', 'F', '5885', 'I', 's']