There are 5 chapters in total in this game and 2 endings. You CAN finish the game without getting either ending.

I have to go out right now, so I'm putting short hand answers to the puzzles, because wow, they're sometimes hard. Any wrong ends (currently) will not be explored. Trial and error it yourself, but I will be putting puzzle solutions immediately. As yeah, there's nothing online about it since release yet.

ALSO - Many of the decisions in this game will be "no choice". ie - you can pick one, but the game will repeatedly cycle the question until you pick the correct one. For example, the first time is in the seance room. You can Ask, or Don't Ask, but the game will basically refuse to let you press Don't Ask, and will loop the question until you press Ask. Again, most of the game is quite linear and you won't be punished for clicking the wrong room (MOST OF THE TIME), so don't worry if you're unsure where to go. Ellie will direct you gently and tell you to pick again. Therefore, unless it's potentially a failure, I won't be adding directions or map selections to this.

CHAPTER 1

BROKEN VIRGIN MARY INVESTIGATION - examine all items. Use Duster. Related to feather. Show Louisa the Duster. It was already cracked. Show the Candle. Show the Candle again. Failure to do this puzzle and prove your innocence gives you a BAD END

Ask Irving about the Key.

ROOM PUZZLE. - Simple. Just take them to the room they belong in. shift tab in game to view this guide at those decisions.
Ms Maahi - Blue
Mr William - Green
Mr Ewen - Red
Mrs Grace - White

Show Mr Ewen the Will then "What is it?" otherwise BAD END

Ask Irving about the Will.
Irving is unfamiliar with Ewen.

Sit with them at the seance.

THEORY - "Those weren't written by a spirit.", the paper was prepared in advance, the words appeared because they were illuminated by the candle. - guessing incorrectly results in a BAD END

Assess the situation - "Go tell him immediately" = BAD END

WINE BOTTLE QUESTIONS W/ IRVING - Wine cork, hole in the bottom of cork, syringe, maurice didn't drink it, handerkerchief. Failure here gives you another BAD END.

CHAPTER 2

Warn him to be careful - otherwise BAD END

LEILA THEORY - Happened during the walk, The evidence is at the opening. Do this incorrectly and you get another BAD END.

Go with her. Otherwise - BAD END.
Run toward him, otherwise - BAD END.

Forest Investigation, USE String, USE Pheasant, Ask Irving.
Forest Interrogation - WILLIAM. Lottery, manipulated it, dangerous, pheasant, oliver, rifle, pouch.

CHAPTER 3

Hall - show Knife holder and Pendant to Maurice.

Predecessors room - Safe Puzzle ANSWER
UPPER LEFT - LEFT 13
UPPER RIGHT - RIGHT 32
BOTTOM - RIGHT 6

Rose garden map - Right, Right, Left - Pink Roses.

EWEN INTERROGATION - Blame someone else, Heard from someone other than leila, show evidence, show diary, Keith, Impersonating, Will + Letter paper.

CHAPTER 4

PREDECESSORS ROOM
Reread Paper, Key: 0, move the hands to 12.

Apple Search - 5th panel, 5th apple in the bottom right. (V=5)

BOX PUZZLE - 326 (upside-down 9ZE)

KNIFE SEARCH
The tea was replaced. Show Natalie the knife.

NOEL INTERROGATION - Questioning, Tea cup shard, tea cozy, black dog.

TRAPPED IN ROOM - Use candle and throw at Ewen out window. Do not jump. Use the bed sheets.

FINAL CHAPTER -

Search SECRET ROOM - Use Noel's note, same letters used, search F, 1 letter before G, Unscrew/use coin.

Search EXORCISM ROOM - Use coin on gap on incense lid, show letter to Irving.

Search DINING HALL - Lift Carpet, Examine Cuck-koo clock, to drop the flame.

VICTOR INTERROGATION - "He's hiding something" Residence Fire, Cuckoo clock and Caramelised onion as evidence, Leila, Silk Thread, To stop the fire.

Putting the correct answers for a full Ewen romance as requested. Follow these and I'm sure you'll get it.
I will not be including bad answers or false questions (questions where if you press one answer, the question will loop until you press the other), or Exhaustive dialogue options (multiple questions that do not matter in order).

- Who are you
- Sit next to Ewen.
- Don't say anything
- Arbirate
- You still have to search his room even during his romance btw
- Eavesdrop (or leave) -> Leave silently if you eavesdrop
- Survey the situation
- I wouldn't say that
- I'm worried about Ewen
- I'm Sure
- Agree
- I can count on him
- I want to follow Ewen
- Follow Him

NOTE: I believe the latest scene on the chart that you can use is right before the final chapter - some point before you have to convince Ewen after Leaving Noel. Every time you select a scenario to start from on the chart, the relationship % for Ewen and Irving will reset to zero (almost as if you're starting as strangers, despite being almost finished with the game).

I have tested these answers with FRESH SAVE only. I repeated everything from the second Ellie arrived at the manor, and no later - so please proceed at your own caution starting from chapter 4, as it is a ways to go before you'll know if it was enough to work.
EDIT: mini-zuzu has found the route works from the beginning of Chapter 3 onwards. As I haven't personally tested this, be careful, but this might work if you want to cut down and don't want to begin from the very first chapter.

To get 4 of the achievements, just play the game naturally and you'll pop them as you advance.

The last two achievements have now been patched and fixed. To get both the "true ending" and alternative ending, literally just romance Irving and Ewen respectively. Both are quite easy to do - just make sure you choose the side of either one you want to romance given the choices. (Some will literally just say "Irving" or "Ewen" so they aren't too difficult to figure out.