for the secret medal, go to the first level of the question mark door:
assign y=260 to a key (in this example we use the down key)
assign gravity and jump (y -=10) to the same key (in this example, the right key will be used)
hold right, and the cube should start to fall slowly.
when it's about halfway to hitting the floor, press down to teleport past the lava and to the door.
the down key only needs to be pressed once, the right key needs to be held down the entire time.
it's possible that using the left/right commands may prevent the medal from unlocking, so don't assign those as they're not needed anyway