There is no evidence to suggest that China urged Russia to delay the delivery of the S-400 missile system to India.
On June 22, 2020, Defence Minister Rajnath Singh left for a three-day visit to Russia to attend a grand military parade in Moscow to mark the 75th anniversary of the Soviet victory over Germany in the Second World War. The defence minister visited Russia days after a violent border stand-off between India and China led to the death of 20 Indian army personnel in eastern Ladakh’s Galwan Valley on June 15.
During his visit, the minister signed another deal to purchase fighter jets and weaponry worth $2.4 billion from Russia. He also held talks with Russia to convince them to rush the delivery of the $5.2 billion S-400 anti-missile system. After meeting Russian Deputy Prime Minister Yury Borisov, Rajnath Singh stated on June 23 that Russia had agreed to accelerate the deliveries.
In 2014, China was the first to strike a government-to-government deal with Russia for purchasing the S-400 anti-missile system. In early 2019, Russian agency TASS reported that China had conducted its first test firing.
There is no evidence or any official statements from any of the three countries that indicate China has attempted to pressure Russia to delay the delivery of the S-400 missile system to India.