When I fill Australia visa form I got a question that ask me "Other ways you spell your name". Unfortunately I have no other way so I think it's better to leave it blank at the same time I fell it must be filled something and I got idea to say none but on the instruction of the form there is nothing that say put none on question that doesn't fit to you, so what shall I do?
Leave it blank, which is what I imagine the vast majority of people filling the form will do. If it's a paper form, drawing a line through the box also works.
Writing "NONE" or "N/A" is also acceptable, but runs a tiny risk of some dimwitted computer or bureaucrat actually thinking your name is None. (See also: Mr. Null.)