How to verify smart contract?

As I was verifying a smart contract using hardhat, I got a problem.

hardhat-verify found one or more errors during the verification process:

Etherscan:
A network request failed. This is an error from the block explorer, not Hardhat. Error: Unexpected end of JSON input

My Questions:

  1. Is there API key like etherscan API key in Pulse? Where can I get it?
  2. What is the apiUrl of Pulse chain? and browserUrl.
  3. If you have a smart way to verify contracts, kindly let me know.