Hi.. The stains due to gutka chewing are extrinsinc stains. If you go for scaling, that is professional cleaning by dentist, he/she can remove the stains and get you back to the original shade of your teeth. However, it is possible sometimes that long-term gutka chewers have stains penetrated deeper into teeth and cannot be removed by scaling alone. In that case, bleaching can help getting a whiter shade and remove stains. I am more concerned about your symptoms of not being able to open mouth fully and burning sensation while eating spicy food. It sounds like submucous fibrosis that is precancerous condition. I advise you to quit gutka immediately and see a professional. Physiotherapy of cheek muscles and other surgical options can solve the problem before it goes in a later stage. Take care. I hope this was helpful. Thank you.