Here is the full list of all 20 Twinsen's Little Big Adventure 2 Classic achievements.
Complete the game
Beat Stanley Opar in the Emperor’s Palace
Reach Island CX
Unlock all items in the game
Learn the Ferryman’s Song
Kiss the frog on the island of the Wannies
Control the crane in the gem mine
Get Baldino to upgrade your jet pack
Find one of the two secret rooms in the Gazogem Factory
Visit the Emerald Moon
Visit the island across the Hacienda and gain the Protection Spell
Acquire the Ball of Sendell
Jump through the hoop in the Otringal dog park
Collect 500 Kashes
Become a wizard
Heal your Dino-Fly
Heal the bowler’s back (warning: his opponent will not be amused!)
Free Joe from his clam in the Cemetery of the School of Magic
Follow the race car driver on Desert Island
Make the rain disappear