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