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