These are the four problems we gave you to solve:

In each case it is White to move and win.
Note that the fourth position is taken from an advanced study composed by Henri Rinck – but without a black pawn on h5 that he had included. That made the problem deeper and more difficult. The full analysis, taken from Harold van der Heijden's database (which contains over 100,000 studies and can be ordered here), is included in our replayer.
Solutions with video explanations