Cars24.com is owned by Cars24 Services Pvt Ltd and they own trademark for Cars24 as well, with Mr Boman Irani as a brand ambassador for this well known brand. They say SELL YOUR USED CARS & GET PAID INSTANTLY !
While Cars24.in is also a operating website but in similar space of Second Hand Cars. The .IN Domain is owned by Mr Atul Dua of Mohali, showing registration date of 3 January 2007, while Cars24.com, which is being operated from Singapore, has a registration date of 05 July 2001.
Therefore, it would be interesting to see,when Cars24.com entered India and was Cars24.in already aware or can be assumed to have knowledge of Cars24.com existence, when it registered the Domain.