@IAS0601 I will answer questions from Your comment through an answer, as it allows for much longer text to be written, and its formatting is much better. I hope this also answers Your original question, but You don't have to treat like the answer. As I wrote, I'm not sure what You are asking about.
1) In practically all cases, GPU accesses images through image views. They specify additional parameters which define how image is accessed (like for example which part of the image is accessed), but still it is the original image that gets accessed. Image view, as name suggests, is just a view, list of access parameters. It doesn't have any memory bound to it, it doesn't contain any data (apart from the parameters specified during image view creation).
So when You create a framebuffer and render into it, You render into original images or, to be more specific, to those parts of original images which were specified in image views. For example, You have a 2D texture with 3 array layers. You create a 2D image view for the middle (second) layer. Then You use this image view during framebuffer creation. And now when You render into this framebuffer, in fact You are rendering into the second layer of the original 2D texture array.
Another thing - when You later access the same image, and when You use the same image view, You still access the original image. If You rendered something into the image, then You will get the updated data (provided You have done everything correctly, like perform appropriate synchronization operations, layout transition if necessary etc.). I hope this is what You mean by updating image view.
2) I'm not sure what You mean by updating descriptor set. In Vulkan when we update a descriptor set, this means that we specify handles of Vulkan resources that should be used through given descriptor set.
If I understand You correctly - You want to render something into an image. You create an image view for that image and provide that image view during framebuffer creation. Then You render something into that framebuffer. Now You want to read data from that image. You have two options. If You want to access only one sample location that is associated with fragment shader's location, You can do this through an input attachment in the next subpass of the same render pass. But this way You can only perform operations which don't require access to multiple texels, for example a color correction.
But if You want to do something more advanced, like blurring or shadow mapping, if You need access to several texels, You must end a render pass and start another one. In this second render pass, You can read data from the original image through a descriptor set. It doesn't matter when this descriptor set was created and updated (when the handle of image view was specified). If You don't change the handles of resources - meaning, if You don't create a new image or a new image view, You can use the same descriptor set and You will access the data rendered in the first render pass.
If You have problems accessing the data, for example (as You wrote) You get only black colors, this suggests You didn't perform everything correctly - render pass load or store ops are incorrect, or initial and final layouts are incorrect. Or synchronization isn't performed correctly. Unfortunately, without access to Your project, we can't be sure what is wrong.
