Nope. Plastic BBs are 6mm- about ,24 inches. Metal BBs are smaller- about .177 inches.
every model is different. But somewhere areound 250 FPS (Feet per second)
Yes it could possible shoot lead ones, or steel ones for that matter but just not at the same velocity as a plastic bullet. They make steel airsoft bbs if that helps you out.
If they are the correct size, you can. I would advise against it.
anywhere from 250 FPS to 600 FPS, depending on the model.