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