Thanks for the response.
With regard to the 2nd question (are window dormers on the roof of the depot building molded into the same piece of plastic of the roof or are they glued onto the roof plastic piece ?), the question applies to both your model & also to boilermaker1's model. Based on your answer above, my understanding is that the modeler has to glue these onto the plastic of the roof, so it is certainly an option to just leave them off. Is my understanding accurate ? Yes
With regard to the 1st question (is the roof of the extended platform part of the same piece of plastic as the roof to the station building ?), that question definitely applies to boilermaker1's model and maybe to your model too. Did your model include the extended platform & depot building in the same kit ? Or did you buy one kit for the depot building and second kit for the extended platform ? The kit came with one extended platform. I purchased three additional extended platform kits. When this model was first offered by Atlas O, the depot building was available as a separate kit (now it is available separately only as a pre-built model, which I do not want). The kits pop up on EBay every so often. I have also seen them for sale at train shows. I wasn't aware that the kits were no longer made. That too bad as hey can be easily modified or kit bashed. The prebuilt don't come with lighting.
For the CB&Q's CB&N style station from the 1950s era, my version will have no window dormers or extended platform. It will have a brick platform with mineral red paint, dark green trim, and the roof will be either dark green or black. It definitely would work and if you can find a kit I would love to see the finished product. If I can come a cross a kit I let you know.
Here are websites that have photos of the two existing stations of the CB&N style:
Thanks for your quick replies !