Here is the full list of all 23 DUCATI - 90th Anniversary trophies - there are 9 bronze, 5 silver, 8 gold and 1 platinum.
Unlock all trophies
Complete your first multiplayer race
Complete 10 multiplayer races
Complete 20 multiplayer races
Reach first place in an event in the Historic Tour mode
Unlock "The 70s" in Historic Tour mode
Unlock "The 80s" in Historic Tour mode
Unlock "The 90s" in Historic Tour mode
Unlock "2K" in Historic Tour mode
Unlock "The Modern Era" in Historic Tour mode
Unlock "The Great Victories" in Historic Tour mode
Reach at least the third place in all the events in the Historic Tour mode
Pull a continuous wheelie for 8 seconds in any game mode
Pull a stoppie for 2 seconds in any game mode
Win a race with Pro physics
Unlock a Title
Unlock all Titles
Reach a total of 6 bikes in your collection
Reach a total of 10 bikes in your collection
Reach a total of 15 bikes in your collection
Reach a total of 20 bikes in your collection
Reach a total of 30 bikes in your collection
Collect all the bikes in the game