If we do Test Drive 4, 5 or 6. Can we use a PS2 since it is Backwards Compatible? Or, do we have to use a PS1 Properly? I just want to know real quick. Just, so I know that I can get the games or not?

You can definitely use a backwards compatible PS2 or PS3. My own runs were done on a PS2.

I've gone and updated the settings for this board so it allows you to specify what hardware you use.