Here is the full list of all 14 InnerSpace achievements.
Collect your first relic.
While breaching the water from dive mode, pass over land before entering the water once more.
Unlock your first airframe.
Encounter the Sunfish.
Encounter the Flock.
Encounter the Leviathan.
Encounter the Warden.
Encounter the Serpent.
Visit your companions.
Collect every relic in the Inverse.
Unlock all planes.
Fly into a world's sun.
Pollinate the Accordion Blooms in the Sunchamber.
Cut down a hanging garden or Windcatcher.