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