Are you trying to pull someones leg?
First, all those questions are covered in the QuickLinkz section. Stroll along and do some reading there - or short and juicy: RTFM!
second:
ad 1. It remains at the place where the bios has put it into memory. If you overwrite the memory in question, the interrupt vector table is gone.
ad 2. The Interrupt descriptor table required in protected mod has another layout than the IVT in real mode.
ad 3. To redirect the hardware irq lines to places in the Interrupt descriptor table which do not interfere with the first 32 entries. the first 32 entries of the interrupt descriptor table are dedicated to Exceptions generated by the cpu.
ad 4. I do it after the switch to protected mode and *after* I have sucessfully installed a General Descriptor Table and a Interrupt Descriptor Table. Do it without those prerequisites and look what happens if you trigger an interrupt. You can do it after installing GDT and IDT as long as the IRQ lines remain masked and you don't generate exceptions.
ad 5. Oh, come on, do a bit of searching: an example you may find on
www.distantvoices.org/html/multitasking.html
stay safe
