why can the same rock layer be found on the top and bottom of an outcrop?

Yes, it is called folding. If you take a long piece of dough, and layer it with other different colors of substance, it will look layered. Now push one side toward the other. the middle will either uplift and form a "hill" or will stay the same level while the dough around it rises to form a "valley". If either the hill or valley sides get too large it will collapse on itself and fold over. Over time the bottom may erode and form an outcropping. You can simulate this by cutting the fold in half. Can you see two lines of the same color?

It's called folding. Take a piece of paper and put your hands on each end and push toward the middle, it will move upward. If the paper is long enough the upward bulge will fall over and it is folded. got it.