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