Forget these discounts-they are very few and only for som tipical stupid touristy things that are way overpriced anyway. In most cases there will be ALternatives that offer better value-you wll nly note these when there. But if-it does not matter what type of pass you hold-they will probably not even be able to tell what is what.

Yes, pass covers ALL TRAIN trips on the systems that accept passes (in FR that is SNCF-the state giant monopoly that runs all, in IT its TrenItalia-there are on main line also private competing Italo=no pass taken). Fast/hi-speed trains all have mandatory RES-paid separetely as surcharge and as most from down yundah seem to believe one has to arrange tis many monthes ahead-complete nonsense, most likely the cause why you got nothing is that you used dates way too early. 2 month advance it should open-plus that around 12/12 is main timetable change here in EUR-no times beyond hat anyway yet

All available discounts can be seen on interrail website here https://www.interrail.eu/en/plan-your-trip/pass-benefits

As well as in the interrail app under More - Benefits.

Some may give a worthwhile reduction but others can be a false economy, always check the official websites and any locally available offers for prices to compare first.