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