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