In the iOS and Android versions of the game, doing all the objectives above ends you up with 101.34% instead of 100%, and if the player complete a task nearly close to 100%, a small congratulatory message appears.
In the PSP version, there are 5 extra Rampages, 3 extra Riding Shotguns, and 4 extra Time Trials.
In many sources, it is commonly said that you need to do warehouse raid at least once to achieve 100% completion, however, this is wrong.
Like in GTA III, there are no rewards for completing the game 100%. A small message will simply appear to congratulate the player upon reaching 100%.