1) To my knowledge there is no ban on trading in bitcoins under Indian laws.
2) If the transaction of sale is carried out as normal business activity, then the profits from such transaction would be offered as income from business. If the bitcoins are held as capital asset, then sale of such assets will attract capital gains tax either long term or short term. If it is done as a casual activity, income from this may be offered as income from other sources.
3) If the apps are sold as commodity as a business, then income from this can be offered abs business income and all the expenses for this can be claimed as deduction against profits from sale of apps. It need not be formal business, but before embarking on selling activity, you have decide whether it is trade or
casual activity once in a way.