I echo @ZeroIndian Even if we give you quick reply ,it will not give you the complete picture. So better start with the varsity modules. Atleast complete the initial portions of it. I am sure your questions will be answered in the initial portions itself and you will also be hooked to read and complete the pending portions
What if the value goes down below 10 lakhs which was my original amount, if it goes down to 5 lakh how can I sell it? Do I need to pay 5 lakhs again to match it with the original amount?
No, if u sell ur invst or stock @ loss then u might end up paying in loss
Is there a time frame that I need to choose when making a long term investment?
No time frame on ur own u can do it
If yes, is it possible to sell it before the time frame?
From all the questions you have asked, it is very much clear that you haven’t read enough about investing. Buying and selling needs a strategy and a trader has to work as per the strategy in order to earn maximum profits. Give a little more time to learning and you yourself will be able to find answers to all these basic questions.