Canon DPP

Wanna ask those that are familiar with Canon DPP.

1. What is the difference between taking (a) JPEG photo and (b) RAW photo, then batch processed it? This is besides the ability to change the picture style & WB.

2. I tried to modify the proceed RAW photos in Zoom Browser, but I think it is not possible. Right?

3. When you cropped a RAW photo, does the picture quality reduce after convert to JPEG?

Thanks.