Your question makes no sense.
Harry Potter, Ron Weasley and Hermione Granger go through a series of challenges to stop Professor Quirrel and Lord Voldemort from stealing the Philosopher's Stone. Harry then has to face both Quirrel and Voldemort alone which results in the death of Quirrel.
Quirinus Quirrel
Ian Hart
Professor Quirrel died in the first book, Harry Potter and the Philosopher's Stone.
Professor Quirrel (Harry Potter 1). Also, his voice was used (modified) for Lord Voldemort.
Professor Quirrel (and technically Voldemort)
Quirrel is the evil guy, in HP1 Who wears the purple-coloured turban.
On the back of Quirrel's head.
Some of them are Professor Snape, Professor Quirrel, and the death eater.
No because Snape was never after the stone. Harry stopped Quirrel (who was acting with Voldemort) from getting it.
No. Although Voldemort is transformed to be on the back of Quirrel's head, Harry does not get transformed at all. If you mean does he change as a character, then yes. Harry develops throughout the book.
Not harry! Some of the people who CAN use dark magic are Professor Snape, Professor Quirrel, and the death eater.