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