I can confirm : Delete all the saves on your ps4, delete trophys pictures, resign the save, then put them on ps4 ( offline )
With the last save : Do the last challenge ( easy way here :
https://www.youtube.com/watch?v=OkUyF0WH7Fk )
With this, u can obtain a
gold medal for the trophy and also unlock maybe 2 or 3 bronze or silver subchallenges )
Then do the last subchallenge ( maybe the gift box for you ), open it 3 time for the bronze medal, then die.
YOu just need 4 bronze with this save to unlock the gold subchallenge trophy.
100 % today, thank you again !