Hi, I am having a problem of itching and running nose and sneezing hundred of times when itching started. Please help?

Allergies... Have you tried taking any allergy medications such as zyrtec, claritin, allegra or benadryl (diphenhydramine). Pick one to try, but if your issues are related to allergies (as it sounds from your description) they should help the symptoms. Take care.
Cannot say. Without an actual examination, I cannot give specific medical advice on your particular health. And... of course there's the conventional over the counter anti-histamines. There's also the possiblity of pathology In the Nose, like a foreign body, polyp, mild infection. each of which would require removal. and... many sttronger allergy meds by prescription (which we can do with our chat service!)
Allergic rhinitis. Itchy watery nose associated with sneezing is usually a symptom of allergic rhinitis. Make notes of when these symptoms occur, to help you identify what might be triggering it. Over the counter antihistamines (Zyrtec, Claritin) may help. Some people are very sensitive to fragrances and fumes, which is another cause.