How am I supposed to inspect these brakes on the pre-trip?(pics inside)

Just keeps rocks and large debris out of the brakes. Never ever have I seen a truck or trailer without them.

 

I rip those dust covers off the truck. You go down a long grade and you'll wish you had. It's hard enough when you're loaded up to max. But you don't add a part that protects the brakes from dust while the dust covers get hot.

 

I think it might be mandatory up there. My truck is the only one I've ever had that had them, and it's a Canuck.

 

Dust covers, sand channels, they go by a couple different names. The position of the brake chamber and the s-cam housing tells you that yes, those are drum brakes.
Here, they tend to be more common on vocational and severe duty trucks... not really a common thing on highway trucks, although Sterling seemed to have a fascination with them. They have the two piece setups, then they have the single piece ones which you need to spiral around the s-cam housing in order to get them off. Kind of a pain in the nuts.
As stated already, you look through the inspection holes. I really prefer not to have them, as they restrict your view of the brake linings, and make it more difficult to catch a seeping wheel seal before it completely blows. For the drivers who actually carry a 32nds gauge and measure their brake linings (or working in a shop where you have to write down the brake lining measurements during a PM) they make it more difficult to measure it that way, as well.
I also think they’re a bad idea for new drivers who aren’t accustomed yet to dealing with steep grades, as they retain heat.