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Yes.
23845
No.
The novel Harry Potter and the Deathly Hallows is in one book.
Seventy two.
The movies -_-
No, the Philosopher's Stone is a different magical object from the Deathly Hallows. The Philosopher's Stone is introduced in "Harry Potter and the Philosopher's Stone" as a stone that grants immortality, while the Deathly Hallows are a trio of magical objects introduced in "Harry Potter and the Deathly Hallows" that represent different aspects of life and death.
All of them died eventually. Everybody does.
They are called fan-fictions, there are thousands of them.
There is no mention of any characters dying afterwards.
There is no book after Deathly Hallows, it is the last.
No, they were just called Harry Potter and the Deathly Hallows parts one and two.