My daughter is very over-excited about many things like she uses her camera every day as if it was just brought. And she always keeps on popping her fingers. Also while sharing funny things with her friends, she gets over excited and talks very fast. She is a brilliant student but ignores her studies,homework and is very stubborn.She gets very angry quickly and does not even apologise for hours together. How can we bring her back to normal?

First of all, how old is she? How long has she been acting in ways you don't like? And what is "normal"?

She is just 12 years old and "normal" means like a studious,respectful.etc

It really sounds like typical 12 year old behavior to me. Mine was the same way at 12.

Yes, you are wanting a 12 year old to start acting like a 8 year old may have.

Children change and at 12 will at times get very emotional, and very excited over things you will never know or understand.

At 12 hormones start changing, there is often interest in boys ( you don't know how many pregnant 12 year olds come to this board every year)

They start looking for and wanting space and freedom, they start fighting back against authority.

So what you described sounds about normal for a 12 year old girl.