Yes, anyone can be hypnotised as long as they want to be and have an ability to concentrate. So it is not appropriate for very young children or people with certain mental disabilities. A hypnotherapist can not force you to go into hypnosis against your will.
This depends on the type of problem and on the progress made. Usually, I see my clients once a week. However some clients come in every two weeks or even once a month depending on their circumstances.
Every individual is unique and different. Some people say that their body feels like a lead weight, others say they feel as though they're floating away. Most people will agree that it's a lovely feeling because they are more relaxed than they have ever been before.
You will be aware of everything that is happening and being said the whole time, however you will be so deeply relaxed that you may find yourself drifting into different levels of awareness. You may forget some of the things said to you consciously, but your subconscious mind remembers everything it needs to. Your subconscious mind is active throughout and it is this that your therapist is working with.
That depends how deep in hypnosis you are, but generally most people do remember either everything or certain parts of the experience. You will find that suggestions which have been given to you in hypnosis will resurface in your conscious thinking mind after your hypnosis session and these will be the thoughts that produce changes in your behaviour or way of thinking and feeling.
The only side effects are the beneficial ones of feeling more relaxed afterwards and feeling more positive about whatever it was you sought hypnotherapy for. Hypnosis is a perfectly natural state.