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