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

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

Q: PoC: What is the ideal length for section 3c. "Plan of the Proof of Concept – Action description the part" ?

R: something aroung 2 pages semm to be a good compromise (assuming that the PI did not change the length of this section before submitting the proposal).