As per IN Digital T&C, it's not that complicated offer, just Ask for an MPEG-4 box from LCO before 31st Dec, 2021 and ask for a Recharge Only with Foundation pack and you're on board for the offer, While you ask for A pay channel or more, you're required to pay channel cost and NCF for that month, The moment you drop those channels, the offer continues.
The only catch is: How much cooperative is your LCO