Same as what I've said before. Merida doesn't have to change, because the "tradition" itself was changed for her. This is no different from Adam/Beast changing in order for Belle to fall for him and break the spell; King Triton changing his mind on humans for Ariel; Powhatan changing his mind about the white savages for Pocahontas; Naveen changing himself for Tiana, Flynn changing for Rapunzel, Aladdin changing for Jasmine, etc. Merida achieved her goal, and got her life back just the way she wanted it. Not to worry. Other princesses don't change, either. So I see exactly the same pattern happening with Merida. Merida learns very little in her movie-- except that spells might be unpredictable. After Merida changes Elinor back into a human, I don't see Merida growing in her mindset at all. In advertising, Merida is "promoted as being the one who fully changes" in the movie, but that is not especially accurate when I watch Brave. It's Elinor who actually changes the most, offering both the new tradition to the clans, and giving "the loophole" for her daughter.

Definitely. The other three have most significant development.

like i said before,Pocahontas´s changes are less significant , again; not a bad thing as she wasn't clumsy like Mulan,selfish like Merida or workaholic like Tiana

Well, Disney totally messed up Pocahontas's story, so she didn't change much.

hers is less dramatic, i guess, though i wouldn't say that she didn't have any character flaws to overcome - her problem was that she was indecisive and lacked direction in her life, and in the end she found it.

what lililc said.

Again she doesn't change.

I don't think she changes. Regresses maybe as someone else said.