Here is the full list of all 10 Eternal Threads achievements.
Save one housemate.
Save all six housemates.
Save all six housemates while also resolving their personal issues.
Open all four locked doors in the house.
Listen to voicemails for all six housemates.
Witness every possible event across all the different timelines.
Read all letters in the house.
Receive a final revelation.
Watch all possible death scenes across all the possible time lines.
Watch all the housemates reveal their secrets.