Trenitalia's web site does not show impossible connections.
REG is a Regionale train, and RV is Regionale Veloce. They are both local trains, but RV makes fewer stops. These trains do not have seat reservations, so if you miss a connection, you take the next train.
Obviously, any form of transport may have unexpected delays.
Train stations have departure screens, similar to those at airports. These show the departure time, the train number (on your ticket for all fast trains), the final destination (which may be beyond where you are going to), and the platform (binario) that will be used.