Malfoy was never really a bad guy. He was raised in a family of Dark wizards, which rubbed off on him quite a bit. He never truly was evil though. Recall, he couldn't kill Dumbledore in Book 6. (Some say its because he was scared but others believe he never truly wanted to. It's probably a combination of both.) So when Bellatrix asked Malfoy to identify Harry, Malfoy didn't tell her the truth because he didn't really support Voldermort. Being *bad* was always expected of Malfoy because of his family history. Malfoy will never have good character, but he will never be evil either.
Dumbledore didn't tell Harry about the prophecy in Harry Potter and the Philosopher's Stone because he thought Harry was too young.
Ariana Dumbledore.
She was Albus Dumbledore's aunt.
Tonks. Albus Dumbledore.
Albus Dumbledore says "of course it is happening inside your head" in Harry Potter and the Deathly Hallows.
Albus Percival Wulfric Brain Dumbledore is his real name.
Albus Dumbledore did.
Ariana Dumbledore.
Albus Dumbledore is male.
Yes, Albus Dumbledore was a mentor to Harry and could be considered as something of a grandfather figure.
Ariana.
Albus Dumbledore
Albus Dumbledore.
She was Albus Dumbledore's aunt.
Tonks. Albus Dumbledore.
Yes, when Harry is in 'limbo' he meets Dumbledore and they talk.
If you mean Albus Dumbledore's sister then it's Ariana. If you mean Albus Potter, then it's Lily.
Albus Dumbledore was killed with a killing curse by Severus Snape.