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