Answer 1

Now these ones are better hidden.

Answer 2

heart heart

Answer 3

a fun one

Answer 4

This level is solid; it has a nice flow compressed into a single screen.  There are only two issues.  First: you can fall forever through the secret quite easily: don't forget death zones around and below the map if there are clips.  Second, sometimes the bricks are "on top" of the rocks and sometimes they're "behind" them because the tiles weren't placed in a consistent order.  It looks weird and could be fixed pretty quickly.