Trains in Italu

Jim,

There's no way to guarantee that you'll have a forward facing seat for the entire trip, since trains sometimes change directions at stops along the way. There are two types of stations, which I call "terminating stations" and "pass-thru stations". With terminating stations, the train enters the station in a forward direction but has to stop when it gets to the platforms - https://www.seat61.com/images/template/background-europe5.jpg . When it leaves, the engine that was on the back now becomes the front engine. With pass-thru stations, the front engine remains at the front during intermediate stops. Hopefully you can see the concept from the description I've provided. The only absolute way to guarantee a forward-facing seat, would be to book two seats facing each other.

For booking tickets, you might consider www.trainline.eu as it's an excellent site. They sell tickets for both Trenitalia and Italo as well as other rail networks all over Europe, at the same price as the networks. Registration on the site including payment information is required, but once that's done, the process is very easy.

You cannot tell. It depends on which way the train was facing when it arriving at the station. Venezia S. Lucia is a Terminus Station, as are Milano Centrale, Firenze S.M.N, and Roma Termini. The trains switch directions every time they pass trough one of these stations. So lets say the train you are taking just arrived from Rome. People who got on facing forward in Rome will suddenly be facing backward leaving Florence all the way to Venice. Then those backward facing seats will be forward facing when the train leaves Venice heading back to Rome. The trains are perfectly symmetrical with an "engine" on each end. At those terminus stations, the driver just walks to the other end of the train and drives from that end.

You can probably switch seats after the train departs, but be prepared to change again if somebody gets on who has reserved that seat. Venice to Florence, the train only stops at Mestre, just a few miles from S. Lucia, so don't switch until then. After that, at Padova and Bologna. Florence to Rome there no stops until Rome Tiburtina, again just a couple of miles, if that, to Termini.

Edit - Remember, if you buy a discount ticket now for Milan to Venice, you must make that train without fail. Otherwise, if you miss it, toss the ticket in the trash bin and buy a new ticket.