1.Megatits quest has multiple "clues" and must be completed at night.
2.One of the scenes is the Megatits one, the other one is obtainable in Ch.3, forgot to remove the (?), same goes for the pics.
3. For the chest at the start of the game, there is a book on the ground in on the same map. That book has a simple riddle in it that give you the number you need to unlock the door.
If you need help during your playthrough write on discord for a fast reply, use the "spoiler discussions" category. We don't check the thread that often.