The simple and straight forward answer to your question is that crypto currency is not a legal tender in India but trading in crypto currency is regulated through exchanges following recent Supreme Court judgment. However, there are indications to the effect that the Government of India may ban crypto currency trading, though the Bank and RBI confirmed that crypto currency is legal in a statement made in the Parliament.
The situation in India is still fluid and lacks clarity on various issues. It needs close monitoring on regular basis. You may follow these interesting articles on trading in crypto currencies in India:
https://news.bitcoin.com/bitcoin-legal-india-supreme-court-verdict-cryptocurrency/#:~:text=Both%20the%20government%20and%20the,Parliament%20Member%20Dr.
https://www.thehindubusinessline.com/news/national/crypto-exchanges-bet-big-on-india/article33175111.ece#
So to say, the future of crypto currency in India is uncertain and challenging.
As regards the tax implications, my views are as follows:
As the crypto currency is not a legal tender in India, the holding of crypto currency is a business asset or a capital asset depending upon the nature of your trading and intentions. Thus you will be liable to pay tax on your income assessed under the head "Income from Business or profession" or under the head " Capital Gains".
In the case of income under the head: " income from business or profession", you will be paying tax on your business income at the rates as applicable to you on slab basis. In the case of capital gains, it may be short term or long term. Short term capital gains are taxable at the rates applicable to you on slab basis and in the case of long term capital gains, it may be 10%, if indexation is not applied and 20%, if indexation is applied.
As you mentioned that you want to trade in crypto currency regularly in large volumes, most likely it will be business income only. You may also have to consider if you want to do this trading as an individual or as a firm or as a company.