Sydney_Guy,
"To what extent NSR process can help reduce anxiety?"
NSR has been shown to be very effective at reducing anxiety. Some psychometric studies are reported in our first published paper. For information on the paper, see
http://www.naturalstressreliefusa.org/research.php. Another psychometric study on the reduction of anxiety using NSR will be published in a few months, and a larger psychometric study on the reduction of anxiety is currently in progress.
"During meditation, is it better to lean on to a chair or just sitting with out leaning on to anything is fine?"
For most folks, it is best to be seated securely in a comfortable chair, with the back supported and the head free to move without hitting any object.
"The reason I am asking this question is that, some times I feel like I get some pain in the neck. Is it something to do with posture?"
It is not possible to answer this question based on the information you have supplied. Certainly, if there is strain on the neck muscles due to your posture, there can be pain. Pain that lasts for just a few seconds can also be a symptom of normal stress release.
"...if I want to do some stretching, is it better to do before or after meditation?"
It depends on the person. Try it both ways and see which is better for you.
David Spector
Natural Stress Relief/USA