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