Definitely plausible for both d) and e). For some reason d) is a very creepy possibility. Certainly if a Type II, III, or IV civilization wanted to remain undetected they could achieve that goal. Some have even suggested that a civilization hundreds of thousands of years old would produce patterns that we might not be able to detect at all. For example, we still do not know what the universe is composed of (e.g., dark matter/energy) and have limited means to detect these natural phenomena. It could be a similar case for advanced civilizations. Possibility e) is just depressing to me. However, I don't believe it is very likely. Even if light is the universe's speed limit we already know of many theoretical ways to circumvent this limit. I would suspect that a Type I or II civilization would be able to figure out how to deal with the light travel issue. Either way, I'm excited for the James Web Space Telescope. We may be able to start to answer some of these questions with empirical evidence!