What is the ERC (European Research Council)? Find more information here:

-ERC website
-Euresearch: the Swiss guide to European research & innovation

Q: Should the team members be identified already at the time of the submission?

This is not required, but the roles/profiles and expertise of team members
required and the distribution of tasks should be clarified in the project
proposal. It should be clear that you are well aware of the profiles of the team members to reach your project goals.