Here is the full list of all 22 Smushi Come Home achievements. It takes around 4-5 hours to unlock all of the achievements on Windows.
Craft every skin
Beat the diver challenge
Unite both capybara siblings
Rescue Chungy
Discover every mushroom
Collect 400 crystals
Rescue both lost lovers
Beat all three glider game challenges
Beat both obstacle courses
Talk to the onion
Acquire all spores of energy
Acquire all wind essences
Cleanse the corruption
Explode the river drain
Beat the nectar gathering high score
Help a friend gather two acorns
Collect 200 crystals
Restore all flower shrines
Knock down all the strawberries
Feed the lizard two berries
Collect 100 crystals
Bring both relics to the researcher