Every variant gets 60:40 split fold seats and rear air-cond vents but that's where the similarities end. Apple CarPlay and Android Auto is available on the E, V and RS variants, LaneWatch is available on the V and RS variants. If you want the best of the best though - including Honda Sensing - then RS is the variant you should go for.
Yes, Honda City is available in Knee Airbags. The available Knee Airbags variants are: 2019 Honda City 1.5 E, 2019 Honda City 1.5 Hybrid, 2019 Honda City 1.5 S, 2019 Honda City 1.5 V.
Yes, Honda City is available in Child Safety Lock. The available Child Safety Lock variants are: 2019 Honda City 1.5 E, 2019 Honda City 1.5 Hybrid, 2019 Honda City 1.5 S, 2019 Honda City 1.5 V.