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.
Cleared Green Hill within one minute.
Got all collectibles.
Cleared all the missions.
Got all custom skills.
Completed all of Sonic's friends' Challenges.
Cleared half the missions.
Got all Red Star Rings.
Performed all of Sonic's actions in Act 2.
Found the spring hidden in GREEN HILL Act 1 and reached the goal with a Red Star Ring.
Cleared CHEMICAL PLANT without entering the water.
Got Rank S in all acts.
Got Rank S in acts 12 times.
Got Rank S in acts seven times.
Chatted with all of Sonic's friends you saved.
Participated in a 30 Second Trial.
Joined the rankings.
Got Rank S in acts three times.
Reached the goal without dropping any of the rings you collected in GREEN HILL Act 1.
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.