Frequently asked Questions and answers to them for the Horizon 2020 programme are published on the Participants Portal:
https://ec.europa.eu/research/participants/portal/desktop/en/support/faq.html
Frequently asked Questions and answer to the H2020-MSCA-ITN-2017 call (Marie Skłodowska-Curie Actions Innovative Training Networks (ITN) are in attached file.