If we label the four elements in the figure as
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; then the arrow at position 1-rotates 45
oACW and 135
oACW alternately; the element at position 2 rotates 90
oACW and moves to position 3 in each step; the element at position 3 rotates 90
oACW and moves to position 4 in each step and the element at position 4 moves to position 2 and gets replaced by a new element in each step.