Your first paragraph ...Hypnosis is an altered state of consciousness, the state of which is utilised to communicate directly with the autonomic nervous system, that part of you that creates inappropriate feelings even when logically you know they are not necessary. Different types of hypnosis are used for different conditions and for different people. They are if you like the tools of the trade which are individually selected.
When in a state of hypnosis the therapist will converse with the unconscious part of the mind, or autonomic nervous system, bypassing the analytical conscious thinking mind. He will converse using various types of hypnosis instructions to elicit a positive response and to eliminate the need to continue with problem or issue at hand. This process may be achieved in one simple session or may take a number of sessions to deal with all the underlying issues.
Assuming the therapist is trained and capable of dealing with any emotional responses that may arise, the process is totally safe.
Very rarely an emotional issue from a persons past may come up to cause the client some distress, the therapist would simply offer to deal with that issue first as it is obviously close to the surface and ideally needs to be addressed. Alternatively the therapist would simply assist the client in locking the issue out of harms away to be dealt with another day, or not.
If you are using hypnotherapy audio programs, you should not drive or operate dangerous machinery while playing these recordings.
The only time a hypnosis audio may be played is if it is a pure subliminal recording and instructions state that it may be played at any time.
Regression or age regression is used to travel back in time to when the causative factors occurred to create a problem. Using various psychotherapy techniques the problems can often be reduced or eliminated. It is often necessary to deal with a number of related incidences which have contributed in causing the final problematic reactions.
A hypnotherapist will often use special words or phrases to allow the client to consider different situations in their mind. By using metaphors or stories the client is guided naturally into a light trance where significant levels of work may be carried out. It may be likened to reading a novel and visualising the story in your mind.
You can utilise the techniques you learn from the therapist to practice self hypnosis at home, it is a very useful adjunct to many treatments and is often used with great success for helping with conditions such as stress and confidence to name but two.
Past life regression and past life healing is the utilisation of regression techniques and taking the process further so that you travel back in time to pre-birth and on into previous lifetimes. It does not matter what your belief as the experience may be viewed in various ways and is often helpful with healing when other options are not working or appear to point to pre-birth issues.
Subliminal practices have been used for many years within the advertising industry to influence the spending habits of large civilisations. The utilisation of subliminal's in hypnosis has been used in audio recordings to enable communication with the unconscious mind without the conscious analysis of each word. This has been used to good effect, and other developments in this field are advancing learning abilities and self help.