Here is the full list of all 50 Flewfie's Adventure achievements.
Open a Treasure Chest
Rescue a Bundrop
Complete the first level
Change Flewfie's outfit using Bunn Bunn's Mirror
Destroy a rift
Rescue Tinka
Deliver Carrot Cake to Bunn Bunn
Deliver all Bubs to Soda Pop
Deliver the missing Ingredients to Soup Demon
Deliver all missing Cogs to Clock Bot
Deliver Shrinking Potion to Scientist Snail
Reunite the friends in the Crystal Plains
Deliver the Crystal Cup to Pinky Panda
Defeat the Leaf Dragon
Defeat Bratty Sprout
Defeat the Grove Spirit
Defeat the Gumball Guardian
Defeat the Toxic Bat
Defeat the Rotten Ruler
Defeat the Shadow Lurker
Defeat Blaze
Defeat the Desert Dweller
Defeat The Keeper
Defeat the Gloom Goyle
Defeat Glitch Bot
Defeat Chrono
Defeat the Cosmic Jelly
Defeat Ruri
Defeat Roze
Defeat Crystelledra
Unlock all Items
100% complete all levels of Cutemelllow
100% complete all levels of the Candyverse
100% complete all levels of the Abandosphere
100% complete all levels of the Lost Towers
100% complete all levels of the Crystal Plains
Win your first game of Fyued
Win a game of Fyued against Glop
Collect all Fyued Cards
Beat all Fyued players at a game of Fyued
Defeat 100 monsters
Defeat 500 Monsters
Defeat 1000 monsters
Defeat a boss with out taking damage
Level Flewfie up to level 25
Level Flewfie up to Level 50
Complete the game on Easy difficulty
Complete the game on Normal Difficulty
Complete the game on Hard difficulty
Complete a level beyond Cutemellow without healing