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