For the people who have read pretty little liars?

I'm wondering a few questions, im a guy. but im really into the series, and new tv show. but i only read the first book. i'm very anxious and i was wondering 1. do the four girls remain friends throughout the book series? i'm hoping so. 2. do ezra and aria stay together through the series?. i hope so again. and 3. after mona dies, who becomes A?... and 4. so alison was NEVER alison..she was her sister?.. woahhhh. PLEASE help. thank you!