A DVD is relatively portable but I suspect you mean a DVD player? In which case it's only portable if it's a portable DVD player.
You can't. But you can play DVDs on a PS2 just by inserting in the disc.
No it only plays movies. but in a way if you think about
well, here is a good site for you to begin your portable DVD player reaseach www.awholesalecompany.com
Sony's portable DVD players only hold one DVD at a time. However you can opt to have a larger screen. The players have screens ranging from 7 inches to 9 inches.