Trains and passes still confused

Sunshine,

Plan to buy regular train tickets for these trips.

Marne-la-Vallée–Chessy to Paris Gare Du Nord and FCO to Rome are both local trains, no discount for advance purchase so just buy on the day at the station.

Rome to Florence and Florence to Milan or Venice are both High Speed trains with discounts for buying in advance. You can look up times and prices on the Trenitalia website ( http://www.trenitalia.com/tcom-en ). Trenitalia is the company running most trains in Italy. Tickets for these trains are specific to a train, and include an assigned seat which is shown on the ticket. Once you buy a ticket, you cannot change your mind and travel on a different train. If you choose a date 2-3 months in the future, you can see the "base" price (what you pay on the day) and the discounted price.
You need to enter the correct names for the stations, NOT the English city name. I.e.: Roma Termini (or "Roma ( Tutte Le Stazioni )" = Any station), Firenze S. M. Novella, Milano Centrale, Venezia S. Lucia.

More info about Italian trains here: https://www.seat61.com/Italy-trains.htm

So what are the local passes for Disney Gare de Marne-la-Vallée–Chessy to Paris Gare Du Nord I have 3 young adults going alone so I want to be able to plan ahead and explain to them what thy have to do since I can't get advance tickets. Thanks again

So what are the local passes for Disney Gare de Marne-la-Vallée–Chessy to Paris Gare Du Nord

Not passes, just normal tickets which you buy from the ticket machine at the station. Price €7.60 from Marne-la-Vallée–Chessy to any métro station in Paris city, or vice-versa.
I looked up this fare on the RATP website ( https://www.ratp.fr/en/titres-et-tarifs/ile-de-france-idf-point-point-tickets ).

Thank you you are awesome :)