Here is the full list of all 49 Sonic Generations Collection achievements. It takes around 15-20 hours to unlock all of the achievements on Windows.
Took no damage while defeating the final boss.
Played Time Attack on all stages.
Got Rank S in all acts.
Got all collectibles.
Cleared all the missions.
Cleared Green Hill within one minute.
Cleared CHEMICAL PLANT without entering the water.
Performed all of Sonic's actions in Act 2.
Got all custom skills.
Got all Red Star Rings.
Completed all of Sonic's friends' Challenges.
Got Rank S in acts 12 times.
Found the spring hidden in GREEN HILL Act 1 and reached the goal with a Red Star Ring.
Got Rank S in acts seven times.
Got Rank S in acts three times.
Participated in a 30 Second Trial.
Cleared half the missions.
Reached the goal without dropping any of the rings you collected in GREEN HILL Act 1.
Chatted with all of Sonic's friends you saved.
Joined the rankings.
Cleared Sonic Generations.
Executed a trick with a seven-step combo or longer.
Defeated 100 enemies.
Got Rank S in an act.
Completed the first stage.