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

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

Q: Can I use special characters in the acronym of the project?

Special characters are not recommended for the acronyms. The main reason is due to IT compatibilities. ERCEA are using different data stores and IT systems throughout the evaluation process, and they are afraid that superscript would not be recognised and properly represented.
We therefore do not advise applicants using such characters.