As the ttl is 255 maximum for ipv4 on cisco routers, will ping work if there are 500 routers between pc1 and pc2?
The TTL field itself in the IPv4 header is 1 byte, which leaves a maximum decimal value of 255 regardless of the vendor of the router.
Pursuant to RFC 1812, the answer to your question is no. Every router is required to decrement the TTL value by 1 whenever it receives an IPv4 packet. You would receive ICMP "Time Exceeded" messages on the source host from which you are running the ping. More information on the TTL field can be found in the RFC.