By all indications it appears Sunny will keep the stripes in her hair but still remain an earth pony.
For the first few seasons, at least. I agree that changing her like that before the series proper even begins is probably not the way to go, but I am kind of intrigued by the idea of an earth pony getting the alicorn upgrade - it would put a nice dent in the whole “unicorn master race” jibber-jabber.
In A Horse Shoe-in, Trixie doesn’t learn anything. She wants something, there are obstacles, she gets what she wants. The end. Despite her causing all this trouble, she still gets exactly what she wants. She whines and complains, and in the end, she’s rewarded for it. There’s no sense of effort from Trixie’s part.
I wouldn’t be surprised if that’s how she got her final position in The Last Problem.
Eh, not quite. Trixie accepts that she wasn’t the proper fit for the vice-headpony position she applied to, helps Starlight find a better candidate (Sunburst), and then is offered a different position (counselor) for which she actually had displayed the necessary skill. Though one could argue that after Trixie’s ill-fated attempt at a field trip, she has no business being trusted with children.