Hi, I'm the one from reddit :-) It's easier for me to write on a computer rather than on the phone (which I use for reddit), so I'll give you some feedback here. I'm not sure I got everything that is possible in the demo, likely not, as I got a bit stuck.
First, I'd recommend a small intro on controls (can be part of the menu, or settings, or even a readme file in the game folder). I see in one of the screenshots that you can get info on items in inventory - how do you do that? Just from experience with games, I guessed "I" for inventory, but I didn't know anything could be done there.
I sometimes didn't get a response when I wanted to interact with something using "enter". For example, in the places where the text "Press enter to enter the room" appeared, it didn't always work for me. I had to move the girl back and forth and then it sometimes worked. I don't have experience with Unity, so I'm not sure what the problem could be.
The rubik's cube puzzle was funny. I guess it is solvable, right? I can't do it for the life of me, so the frustration result amused me (at first I thought it's some kind of bug).
Sudoku and puzzle pieces were fine. I'm not sure, since you said some music is still to be added, if the silence during the puzzles is deliberate. If it is, maybe I'd recommend at least a couple of sound effects (like when the puzzle pieces fall into place, or when you fill in the sudoku number).
I'd also recommend when the girl interacts with things and the comment is longer, like her desk and the text about meals, to change the text into something shorter once the player has already seen it. The shorter texts, like the one about her clothes in the wardrobe, are fine, since they don't take that long.
In the father's room, there's text about a key in a coat, which comes sort of out of nowhere (I had no idea there was a coat), maybe add more context there.
Lastly, when I returned to the girl's room for the second time, the mouse cursor appeared. It wasn't visible in any other screens (besides the puzzle ones), so I guess that's something that wasn't supposed to happen. I could move it, but clicking didn't do anything.
I probably didn't do something I was supposed to do and was a bit stuck, but what I tried made me curious. Keep on developing!
(And one more thing, I have to agree with the other redditor, although Lost Memories is a good title, there are too many games here on itch with the same one, so maybe try to add something to make it distinct from the others.)