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