Well firstly, I am not from DreamHost support, but, since this is primarily a customer to customer support forum, I will do my best to answer your questions.
Yes absolutely. In fact, you can host anything you desire as long as the content is legal according to the laws of the United States.
DreamHost does not use cPanel. They use a custom written admin panel that, in my opinion, is superior to cPanel. If you are coming from a cPanel based host, you may have a little difficulty becoming accustomed to the DreamHost panel, but after a while you will appreciate the extra functionality provided.
Yes. If you sign-up for a plan at a particular price, that price will remain unchanged for as long as you maintain that plan. Also, you will receive any increases to storage space and bandwidth that may be added to your plan during your time here.
edit: Just to add to the above; If your plan price decreases during your time here, you will be able to move to the new lower price.
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