Is there a difference between "in-place" and "space complexity O(1)" or do they mean the same?

Question

Do in place and space complexity O(1) mean different things? If yes, can someone explain the difference?

Answer 1

Space complexity of O(1) is a stronger requirement than in-place, because O(1) implies that the changes are done in place, but not the other way around.

You can make an in-place algorithm that has a space complexity above O(1). For example, the recursive re-heapifying algorithm of Heapsort is in-place, but its recursive implementation without tail call optimization has an O(log N) space complexity.