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.
Cleared Sonic Generations.
Got all custom skills.
Got all collectibles.
Got all Red Star Rings.
Got Rank S in acts seven times.
Cleared CHEMICAL PLANT without entering the water.
Found the spring hidden in GREEN HILL Act 1 and reached the goal with a Red Star Ring.
Cleared Green Hill within one minute.
Reached the goal without dropping any of the rings you collected in GREEN HILL Act 1.
Chatted with all of Sonic's friends you saved.
Cleared all the missions.
Completed all of Sonic's friends' Challenges.
Cleared half the missions.
Executed a trick with a seven-step combo or longer.
Defeated 100 enemies.
Got Rank S in acts three times.
Got Rank S in an act.
Completed the first stage.
Got Rank S in acts 12 times.
Got Rank S in all acts.
Performed all of Sonic's actions in Act 2.
Took no damage while defeating the final boss.
Joined the rankings.
Participated in a 30 Second Trial.
Played Time Attack on all stages.