Here is the full list of all 17 Forgotten Fields achievements.
Begin the journey back home
Try on a new outfit
Steal Mr. Jacobs' keys from Mr. Fernandes' table
Get the keys by telling Mr. Fernandes the truth
Successfully fix Sid's bike
Pet Ethan's dog
Knock the football out of the tree
Recover and return the laundry to Ethan's mum
Relive both camping memories
Go for a swim at the beach (when in 3rd person)
Spend 5 minutes or more swimming at the beach (when in 1st person)
Reach home
Entertain Sid's friends at the dinner party
Get back to work
Encourage the Knight to return to his time
Sell the house
Keep the house