Create a function that takes a list and a number and selectively reverse the order of the list based on the number you're given (second argument). If you're given the arguments [1,2,3,4,5,6] and 2, you would return the list [2,1, 4,3, 6,5].
sel_reverse([1,2,3,4,5,6], 2) ➞ [2,1, 4,3, 6,5]
sel_reverse([2,4,6,8,10,12,14,16], 3) ➞ [6,4,2, 12,10,8, 16,14]
sel_reverse([5,7,2,6,0,4,6], 100) ➞ [6,4,0,6,2,7,5]
length exceeds the list length, reverse everything.length is zero, return the original list.