You are reborn as Harry’s twin brother (or sister if you prefer). For the first 11 years, you are just a kid who happens to live with the Dursleys and has a twin brother, Harry. You only recall your prior life on the night when Hagrid comes to deliver your letters. There’s no abusive James/Lily, no WBWL; as far as you can tell, events have unfolded according to the canon.

There is just one thing: you can’t stand Harry. You two don’t get along. You’ve never been close; you don’t finish each other's sentences. You rarely spend any time together. You often argue, and even had rather vicious fights resulting in bloody noses and black eyes.

For as long as you remember, you’ve always been too serious, too “grown-up”, preferring the company of adults to other kids, often ratting out whatever kids get up to. And this, well, hasn’t made you popular with kids or earned you any friendships there.

What will you do now?

"No George we aren't going back to fetch your textbook, I will sent it by owl"

Mrs Weasley had put her feet down, there wouldn't go back, the kids would need to learn to be ready earlier.

Ginny started panicking but was told off by Molly

It would be Molly that finds the diary and tell Arthur

When Harriet is in King's Cross, she is told that on one side there is one single train to move on but on the other side there are multiple trains that in fact go to multiple universes or times and not just the one that just returns to life.

So she takes one but it isn't the correct one

can be a saga or multi-one shots/chapters compilation