Here are all four puzzles, annotated, in our replay window. You can click on the fan button below the board to switch on an engine to answer any residual questions you may have. Click on the blue arrow to the right to access the list of studies.
And here are video explanations of the studies, presented by Brainy:
The third video contains a discussions of endgames three and four.
Were you able to solve these studies by yourself, were you able to grasp the salient points they encapsulate? That will enhance your skills in similar endgame position you might encounter during your games.