You will need to have a playable character no matter what, but that doesn't mean you need to create any sprites for it. Delete all animations except for one of the idle animations & create a transparent png or webp image about 100x100px or so & assign that image to the idle animation you didn't delete & now you have a character that's invisible that you can assign interfaces to.
1. Depends on if you plan on having playable &/or non-playable characters in the scene as the way system is used for determining the scale of characters at different positions in scenes.
2. You can use the display narration text action part.
3. You still need to have a playable character, no matter what.
Additional information...
a. The playable character shouldn't have to be in the scene to acces the command interface or inventory, but it's probably best to have them in the scene anyway for save game reasons.
b. You should also disable centering on the playable character (via the center scene on character permanently action part with the option unticked) to prevent the viewport camera from trying to follow the playable character around.
c. For the position for the playable character you can put them anywhere in the scene, but I would recommend drawing a small way system border outside of the scene & placing the character inside of that so it's out of the way.
d. You can force text position via event handlers/listeners, but those require a little bit of scripting. However display narration text action parts are probably more than enough for what you need as you can manually specify which font to use & where to position the text.
e. For a first person game (visual novel, myst-like, hybrid, hidden object) you will need to create & use immediate execution type commands instead of at destination type commands because without a moving playable character, the at destination commands won't work.
f. in the main game settings > mouse properties section, you can prevent left mouse, right mouse, etc. from updating the destination position, which is probably something you should disable for first person p+c games.
Anyway, I think that about covers everything you asked. Also feel free to join our discord server if you want @
https://discord.gg/g5zFejW
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