Here is the full list of all 20 Doodle Tanks achievements.
Unlocked all elements of Germany
Maus created
Unlocked the PaK 44 L/55 and KwK 44 L/38 guns
Unlocked Panther, Tiger I, Tiger II
Bölter created
Unlocked the Pz III and Pz IV tanks
Unlocked all Germany events
All TDs created
All USSR elements unlocked
All medium tanks created
T-34, KV-2, IS-4 tanks unlocked
All light tanks created
All inventions created
All T-34 unlocked
50 elements unlocked
All Lend-Lease supplied tanks unlocked
First tank created
8 groups created
25 elements unlocked
T-34 unlocked