You can use the sample tasks from manifest file to perform local testing. See instruction on how to get sample tasks. To emulate the validator, have a look at the Validating instructions.
Where can I see my scores and other metrics?
Each competition has it's own dashboard demonstrating relevant metrics. You can find them on the Apex website at apex.macrocosmos.ai/ in the competition section. Also Apex CLI provides a set of metrics for the competitions.