Whether I can program the address range from C0F000h to C0FFFFh of Flash 0?
Ok, I don't know why my last post didn't work but here it is again...
RESERVED means you cannot erase it, program it or access it.
You should add the following entry 0xC0F000-0xC0FFFF to the Reserve line on the L166 Misc tab.
Perhaps I don't fully undersand your question. Why do you feel that you need to touch this 4K range?