All good points. Let me add a bit about languages. Even on earth, we have languages that use tongue-clicks or whistling to express phonemes. That still assumes "hearing" which is perceiving sound waves within a certain range of frequencies. A certain part of language is conveyed by body language and facial expression also. What is aliens had different sensory apparatus? If their bodies are structured differently, or their environment is very different, might effect mental concepts of the universe, which is the basis of language.