Yes you'll get Interrail and them Eurail.

Seat reservations are required on some trains. They can be bought at the same time (so you sit together) using any other website than interrail.eu/eurail.com, have a look at https://www.seat61.com/interrail-and-eurail-reservations.htm

Have at look at this helpful page for rough itinerary ideas : https://www.seat61.com/Greece.htm

There are no international trains from/to Greece so you could either take a ferry from Italy or a bus from Bulgaria.

Don't hesitate to come back!

Thank you for the quick reply!

This may sound stupid but I feel the need to ask this anyway, is it possible to get a train from Thessaloniki to Athens?

Thanks!

Trains should be running between the two but I don't know the exact details. There are disruptions since the deadly crash on that stretch on 28th February 2023 (57 deaths).

The security systems to avoid such crashes were not enabled so I wouldn't necessarily trust trains in Greece right now (my personal take). They had been fined by the EU for the disrespect of these basic security rules too.

There are currently 4 trains/day in both directions between Thessaloniki and Athens. Timetables on https://www.hellenictrain.gr/en but the timetable module currently only seems to work with a VPN set to Greece. You need a reservation (it's free of charge), which you can only get at a ticket office in Greece.

Perfect thank you both for your replies :)

1 more thing hopefully you see this, does interrail and eurail use the same app? My australian family member is nervousn that we might find issues getting on the same trains using different services. I know interrail and eurail are the same company so im hoping they use the same app for your pass.

Thanks!

Both Eurail and Interrail use Rail Planner app. This is the place where you activate your pass and log each train you're taking as you go. Each one of you will have the pass on its own phone.

Reservations cannot be made there. It's recommended to make them elsewhere than through Interrail/Eurail websites to save booking fees (and in your case to make sure you sit together), through the railway company directly whenever possible.

Onboard you show both the app (QR-code, your ticket) and the PDF (seat reservation).

Have a look at these 2 links :

https://www.seat61.com/how-to-use-a-eurail-pass.htm

https://www.seat61.com/interrail-and-eurail-reservations.htm