The following is based on the True End path:
Visually, I liked the softer art of Alex's sprite and how it contrasted with the pixelated BGs: The former has an almost children's-book quality while I liked the retro colors and aesthetic of the latter. It was almost muted retrowave, like the game was invoking early DOS games, including the GUI. The art of Spongeblob made me chuckle; I'm pretty sure I used to draw that way too.
Story-wise, it felt like an educational game (in a good way!) to teach kids to use the Internet or older players (family, teachers) to guide kids into using computers. I don't know how old most kids are today when they start using a computer, but I don't find it implausible that they lack one or that Alex hasn't used one since the MC presumably doesn't have money to spare. It also felt as though the game might be set earlier than the present, when computers/the Internet wasn't as common; that impression might be due to the retro graphics, but the MC mentions that the computer is one that 'every spoiled kid' would love, implying that computers are an expensive luxury rather than relatively affordable/attainable.
I think the game could benefit from a line or two explaining the characters' living situation: While it didn't detract from my experience I was confused as to where and how the MC and their sibling were living, especially since the entire beginning is about how they're estranged from their parents. Aside from the parents gifting Alex a computer, it seemed a little extraneous to the rest of the story. I was surprised that they went to an Internet cafe, but this might be regional: Where I live it's common for people without computers/the Internet to use library computers since Internet cafes are less common and cost money, but it might be otherwise elsewhere.
It was obvious how much the MC cares for their sibling and that they have a strong relationship. I appreciate that you had a variety of answers/attitudes as responses and that the final choice didn't have a "perfect" option; I liked Alex's willingness to speak up for themselves, presumably because trust was at max. Alex's friend being nonbinary and Alex potentially being nonbinary was straightforward without being heavy-handed and I liked that Alex was able to relate to the concept through Squareblob, similar to the way many young children learn about complex ideas. It felt a little nostalgic, as an older sibling, and I agree with the idea that that young children need guidance to use the Internet safely: Children absorb ideas quickly and don't always know which are good or healthy, so letting them onto the 'Net without initial supervision could lead to learning and internalizing harmful ideas. Being able to help Alex become more confident with a computer, and be a supportive sibling was genuinely heartwarming.
It did seem a little odd that you couldn't choose the gender of the viewpoint character, especially as the game is so careful about not using gender-specific pronouns for Alex. The game description doesn't mention that the MC is male and you only find out when Alex addresses you as "Big brother," so the ability to select your gender or some earlier indication that you're male would be nice. Overall I found the game charming, with a natural-feeling relationship between the siblings and and worthwhile messages that didn't get too heavy-handed. Sorry about typing so many words for a relatively short game, but you clearly put time and effort into this and it shows!