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.

there is no scientific basis for Gnosticism or orthodox (mainstream) Christianity.

Neoplatonism is based on the teachings of Plato and early Platonist. Neoplatonism is a modern term for Mystical Philosophy that came about in the 3rd Century.

"the birth of Venus" and "Primavera" are his most famous works of art, which gave the world the concept of Neoplatonism(VERY RADICAL IDEA)!

More information on Neoplatonism at link below.

Yes!