For entry to Italy, one of the conditions of the Green Pass will be sufficient: certificate of vaccination, certificate of recovery or negative test result. https://www.governo.it/en/covid-19-travel-information
You need to show your CDC white card or an official recovery certificate issued by government or state health authorities, when asked for the super green pass in Italy. If your vaccination or recovery certificate has a QR code, it can’t be read by the Italian app that scans vaccination certificates, so your certificate needs to be read manually. Be advised that not all restaurant and venue owners in Italy uniformly recognize vaccination certificates that cannot be scanned by the Italian system; however, this FAQ on the Italian government on its green pass website (in Italian only) states that US vaccination and recovery certificates are valid as super green pass equivalents in Italy. More information for US travelers about CDC white cards as super green pass equivalent at the US Embassy in Italy Covid-19 information page.If you have your CDC White Card showing your vaccination, this will be accepted in all establishments that require a green pass.
No. The super green pass requirements apply to everyone in Italy age 12 and over.