Can diamond dude's effect bipass every card cost?

Question

example: destiny draw, trade in, allure of darkness, etc.

Answer 1

Yes, it can bypass any normal spell's cost. However, removing a dark monster from play is Allure of Darkness's effect. You will still have to remove a dark from play. Allure has no cost.

Answer 2

Yes, it can bypass the cost on any NORMAL SPELL card that he happens to flip up.