What religion studies the Qur'an?

Answer 1

ISLAM is the primary religion that uses and studies the Qur'an قرآن as its primary holy book. There are other Post-Islamic Religions like Baha'i and Druze, which developed out of Islam (hence the term Post-Islamic) that have high regard for the Qur'an and do use it on occasion, but only as a lesser source to their own unique holy books. (In the case of the Baha'i, the key holy book is the Kitab-i-Aqdas كتاب الأقدس and in the case of the Druze, the key holy book is the Kitab al-Hikma كتاب الحكمة.)

Answer 2

Mainly Islam.

Answer 3

Only Islam.