Downwell

You need to complete a level without landing on any platform. Timevoid caverns and shops count toward this trophy, so even landing inside the timebubble will void it.

You can try it in any level, but the easiest place for sure is on Area 4-1 on Normal. Start the level avoiding the first platform and proceed to finish the level not entering any cavern and landing on any platform (even those covered with red spikes). Just remember that when you start Area 4, there will be a platform where you can land.

You can try it on other levels, but it's way harder, since there are many platforms and ledges you can land on accidentally, and on top of that you have enemies to deal with (I did this on Area 1-1 and can confirm it's WAY harder).

The trophy will unlock at the said level upgrade selection screen.