I see thats an A350 for this route.
- Infant on Lap - I think I have seen videos where the baby can easily fit in the A350/A380 long haul seats
- Car Seat - If you plan to bring a car seat in the plane then I believe you have to purchase a separate seat
I myself am flying with an 18 month old infant end of this month SFO - SIN - BOM so I can share my experience with you then :-) I am planning to sit him in our seat/lap. Hopefully he takes a lot of naps !