Very noob customisation questions.

I have a dark purple rg450 that has a deep scratch on the back. How do i fill this (about 1mm) and how do i know what and where to get the same paint etc?

The screws (pickguard etc) are a little oxidised so looking to replace them, but want to spray them a lighter purple, should i use ordinary spray paint?

The mirror pickguard has some scratches, any way to restore this?
Leave the scratch, you're only going to make it worse by attempting to fix it. The modern poly finishes on Ibanez's do not accept touch up repairs easily. Leave it, unless you want to make it look worse. If you're reall intent on attempting to fix it go to your local auto store and bring your guitar. They should have touch up pens there and see if you can match the color.

You want to paint the screws? Ordinary spray point would work, but you may want to look to get an adhesion promoter to spray on the screws before you spray the color. I'd also be cautious when screwing them back in as you run the risk of chipping the paint off easily.

Just leave the pickguard, you'll only make it worse. It's most likely plastic and plastic is hard to buff out.
'Aim at perfection in everything, though in most things it is unattainable. However, they who aim at it, and persevere, will come much nearer to it than those whose despondency and laziness make them give it up as unattainable.'
i have some plastic polish (used for ipods etc) that might work.

the scratch looks awful, its white.