Help regarding tax for student who is into stock trading

I need some help in knowing the tax system in India. I am a student. I do some freelance work through which I earn not more than 12k a month. I recently started stock market trading. 

So I want to know if I will have to pay any taxes. 

Also - 

If say I buy a stock at 200 and sell it at 205 (intraday) and I make a profit of ₹5. So I want to know will they take ₹5 (that is the profit) or the full value (200+205=405) for the calculation of under ₹2,50,000 tax slab which has "No Tax" rate?