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.
Cleared Green Hill within one minute.
Got all collectibles.
Got all custom skills.
Got all Red Star Rings.
Played Time Attack on all stages.
Joined the rankings.
Participated in a 30 Second Trial.
Found the spring hidden in GREEN HILL Act 1 and reached the goal with a Red Star Ring.
Got Rank S in all acts.
Cleared all the missions.
Got Rank S in acts 12 times.
Completed all of Sonic's friends' Challenges.
Executed a trick with a seven-step combo or longer.
Cleared half the missions.
Cleared CHEMICAL PLANT without entering the water.
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.
Cleared Sonic Generations.
Performed all of Sonic's actions in Act 2.
Got Rank S in acts seven times.
Defeated 100 enemies.
Got Rank S in acts three times.
Got Rank S in an act.
Completed the first stage.