Can some one please help me.
a) If i buy Bitcoin through Credit Card in USD and Sell in INR (on Indian exchanges ) i.e trading , so will thier be any problem with income tax/RBI ? becoz transaction size will be huge ,and lot of money money in and out of bank account. i am ok to pay taxes. But i am worried about FEMA/and other un-necessary torture by IT/RBI.
Please help. I am unable to get answer anywhere

Income tax won't be a problem if you declar/pay tax. RBI maybe a problem as USD to INR conversion has happened.
Best case scenario - RBI ignores or issues warning. It has work to do.
Worst case scenario - RBI penalizes you 3 times the amount.
Just my 2 cents.