1. Yes and No. When you are 100% in the astral body, you experience a loss of touch, taste, and scent. Although, you may be able to maintain these senses IF you are in a state of "dual-conciseness" (50% astral, 50% physical)
2. You can breathe, and cough, but these are physical functions so you will not feel that you need to do either.
3. If you mean enter other landscapes and cross dimensions, then yes.
4. Anyone can astral project.
5. Yes/No. Your mind will be awake but your body will be sleeping. This is why you enter paralysis, while still in a state of consciousness.
6. No. Once again your body is paralyzed. If you think of your dense body too often while in astral form, there is a possibility of returning.
7. There are a variety of multi-dimensional being's. All are benevolent. Many have been able to talk to the dead, although that will usually only occur when that specific person is a spirit guide. Negative "entities" may appear, this is just energy, and can easily be cleansed by sending rays of light.
8. No, the chord will snap when your physical body dies.
9. No idea.