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.
Completed all of Sonic's friends' Challenges.
Cleared half the missions.
Played Time Attack on all stages.
Got all Red Star Rings.
Got Rank S in all acts.
Chatted with all of Sonic's friends you saved.
Got Rank S in acts 12 times.
Cleared CHEMICAL PLANT without entering the water.
Found the spring hidden in GREEN HILL Act 1 and reached the goal with a Red Star Ring.
Took no damage while defeating the final boss.
Cleared Green Hill within one minute.
Got Rank S in acts seven times.
Joined the rankings.
Participated in a 30 Second Trial.
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.
Cleared Sonic Generations.
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.