Spoiler :) She was because she thought it would help her become a better warrior but ever since Dovewing Jayfeather and Lionblaze talked to her and told her that they're bad and made Ivypool a spy she only does it because of spy missions.
No. He is dead. She is alive. He was (and still is) a tyrant trying to take over the forest, and she is just following him.
He tricks her by telling her no one cares about her, that she isn't special like her sister, and that she doesn't need Thunderclan to be great.
Hawkfrost gets killed in Sunset. Book 6 of the new phophocy
She isn't told, but she over hears Tigerheart and Tigerstar talking. It reviles that Tigerstar had been lying to her. He was not helping thunderclan.
They both will become warriors in Sign of the Moon. Dovepaw will become Dovewing Ivypaw will become Ivypool
I dont know. She is really upset about how her sister is getting all the attention and is being a real pussy cat! Inside she is a good person, she just needs to be more relaxed and work out her problems. In books later on, Ivypaw is visited by hawkfrost, but she doesn't know he is evil. Hawkfrost tricks her into doing something horrible-- something you will have to find out-- but anyways he tricks her, and this causes a very horrible death.
They become apprentices in The Fourth Apprentice.
Theres a big battle between shadowclan and thunderclan(which Ivypaw suggested). Firestar dies and Russetfur is killed. Also, Tigerstar and Hawkfrost meet Ivypaw in her dreams, teaching her new moves. Tigerstar was the one who told Ivypaw to convince Firestar to start the battle. Theres other stuff but you need to read for yourself.
Not really, when HawkFrost sliced his belly open and then when IvyPaw saw that white cat with a scar on his stomache that was SnowTuft. Improvement: It was really Shreadtail who sliced Snowtuft's belly open.
Dovepaw is the chosen one not ivypaw. ( I thought ivypaw was one of the thrre)
Tigerstar, Darkstripe, Scourge, Ashfur (maybe) ,Hawkfrost. There might be more, but that's all that I remember. [those are correct, but there's also Brokentail/star. Bone. Thistleclaw. I think Ivypaw may be becoming bad.]
The New Prophecy, Book 6, Sunset