Here is the full list of all 69 Returning To Mia achievements.
Collected all other achievements
Turned Isla down
Didn't go inside with Sadie
Picked Mia over Sadie
Found all four endings
Ended up single
Talked to Hope for the first time
Reunited with Sadie
Didn't turn Isla down
Chose Mia forever
Went inside with Sadie
Got slapped, hard
Got rid of the towel
Agreed to come to Giselle's office
Picked Sadie over Mia
Told Cindy you are interested
Told Cindy the truth
Relaxed AGAIN!
Thought about Vivian
Thought about Cindy
Thought about Isla
Thought about Grace
Thought about Mia
Got to know Cindy better
Gave good advice to Isla
Unlocked the gallery
Rushed to Sadie in a time of need
Proposed to Sadie
Had to make a "difficult" choice
Trained with Mia
Failed to dodge properly
Lifted an EXTREMELY heavy box
Helped Grace out
Found a mysterious note
Chose not to stay with Mia
Chose to stay with Mia
Used the "Two in one" button
Accepted Simon's proposal
Refused Simon's proposal
Spied on Ellie and Vivian
Talked to Pete for the first time
Admitted you have fantasies to Sadie
Complimented Mia's costume
Used the back door
Kissed Isla
Had to change pants
Took Sebastian's pants
Became a "Spartan"
Remembered your past with Mia
Met someone familiar
Went looking for Sadie
Talked to Giselle for the first time
Talked to Sadie for the first time after a while
Went to dinner with Grace
You relaxed!
Found out Mia want you to stay
Got rid of a bully
Talked to Isla for the first time
Found out Cindy is Sebastian's daughter
Talked to Sebastian for the first time
Talked to Cindy for the first time
Flashback!
Talked to Mia for the first time after two years
Used the "Angle button" once
Talked to Grace for the first time
Used a certain little red button
Talked to Vivian for the first time
Started the story
Used the "Panic button" once