It does come with a rain cover located in the small pocket on the back side of the pack. I would imagine it would hold that size of laptop as I carry my Surface along with a large expandible folder with important documents I need to have for hockey tournaments.
The compartment that has the camera actually has two zippers and you unzip them completely to fully open the bag. You can just open the zipper partway and grab your camera, but if you need access to another lens you will need to open it fully. The small pocket on the side just holds small items like SD cards and a pack of gum, something small like that.
In my experience, it would be difficult to access the camera without opening it from the top. I typically shoot with a Tamron f2.8 70/200 and with the size of that lens, it would be impossible to configure this pack to pull it from the side.
Hi Annie - The Case Logic DCB309 has an adjustable divider system that allows for customizable organization. Depending on the size of the lens, 2-3 additional lenses, a flash, and other camera accessories can be housed in the SLR backpack. It is the decision of the user to configure the pack what suits them best. Enjoy!