Yes it is legal to trade bitcoins in India since government never announced any ban related to crypto holding or trading but using bank accounts in India for trading will get you in trouble since banks restricted crypto transaction so you can't een deposit into any exchange and trade cryptos but you can use p2p sites like localbitcoin to trade bitcoins.
Recently binance also launched something called Binance Wazirx in India to deposit fiat and trade cryptos.
of course it is very special for India because it has been given facilities by binance for transactions to be fiat and maybe there are also many parties who can provide these facilities. all because it is natural to get it, they are countries that are actually very advanced technology and should be able to use crypto. but it must also be recognized economically that it is still experiencing difficulties because there are still many that need to be assisted by the state. so the state still needs to adapt to crypto transactions, even though the state can play a role there to be able to take taxes.