Q9) Could be an easier one

It comes in various forms and each has its own effects. These include White, Pink, Red, Blue, Black, Silver, Gold, Jewel, Slow, Magno etc. Synthetic versions have also been made with their own effects. Despite the matching name, it was never suggested that X had any connection with Y, though this now seems to be the case. Long term exposure to X can have adverse effects on humans and can lead to cancer. ID X

The Answer is Kryptonite: "Kryptonite is a fictional element from the Superman mythos. Despite the name, it has no connection to the real chemical element krypton."

Aishwayra, Anannya and Namratha got it right in that order.