Gnostocism flourished during the early years of Christianity and, in the view of some scholars, may have accounted for around half the Christian population. What was to become the dominant branch of Christianity, Catholic-Orthodox, persecuted Gnosticism out of existence in Western Europe, although it continued in eastern Europe. The Cathars were a sect with strong Gnostic influences that re-established a presence in southern France in the twelfth century, but was once again eliminated by the Catholic Inquisition.
Modern Cathars claim to be survivors of that purge and to maintain original Cathar beliefs.
The Rosicrucians are a legendary and secretive order that appears to have been founded in the 15th century, the 17th century or perhaps the 18th century. While it probably can not be described as genuinely Gnostic, it does claim some Gnostic influence.
Gnosticism can be read about in many books. The Gnostic Society has their own Library in which everything about the Gnosticism can be learned or studied.
They practiced over and over again to start and now there good They practiced over and over again to start and now there good They practiced over and over again to start and now there good
there is no scientific basis for Gnosticism or orthodox (mainstream) Christianity.
Islam is now practiced all over the World now.
The opponents of Gnosticism were primarily early Christian leaders and theologians, such as Irenaeus and Tertullian. They argued against Gnosticism's belief in secret knowledge and its rejection of the material world, emphasizing instead the importance of orthodox Christian doctrine and the belief in a loving creator God.
Buddhism began with the Buddha in about 440 BCE and has been continuously practiced from then until now.
Simon Magus
Gnosticism does not have a single founder as it emerged from diverse religious and philosophical influences in the ancient world. However, it is believed to have been shaped by various early Christian and Jewish sects, as well as elements of Hellenistic and Persian mysticism.
I/we/you/they have practiced. He/she/it has practiced.
Pneuma
Islam is mostly in iran now
No book in the bible addresses Gnosticism, you are looking for Against Heresies as written by a father of the church, Irenaeus.