Forex futures & options is already legal in India because it is regulated and monitored by SEBI & RBI respectively. Spot forex (24x7 forex) is basically over-the-counter & decentralized in nature so unlikely to be considered legal in India.
Besides, with FX futures trading, information about liquidity, volume and pricing is consistent across brokers and trading terminals. With spot forex, price and volume are what the market maker says they are. So, unless you've got a STP or ECN broker, the chances of a bucket shop broker taking the other side of the trade is high in unregulated spot forex.