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