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