Here is the full list of all 7 Into the Sinkhole achievements.
Player has started ‘Into the sinkhole’.
Started the game in Strawberry mode.
Started the game in Watermelon mode.
Player has completed the game in Strawberry mode.
Player has completed the game in Watermelon mode.
Player has completed the game a second time.
Player has stepped on the platforms 1000 times.