How to completely track a plane, not a flight? This probably has already an answer somewhere, but probably don't know the proper search keys to find the information.

Out of curiosity today I was trying to track a flight: one of my friend texted me about her flight being a lot late, and for fun I wanted to try to see if it was possible to understand what caused the delay. I knew flightradar24 by fame and found too flightaware by chance; I tried with the flight number (EZY2604...if this is the flight number) and couldn't find many information, 'till I realized that EZY2604 is probably something like the callsign for the route plus the scheduling, so with that I can only find details for this combination. And I can only track a plane which is flying, it seems.

TL;DR: how can I go from a flight number to the full route of the physical plane in the previous hours?
If you want to look for the airplane that flew a certain flight (U22604/EZY42EA for your case), you could go onto flightradar24.com/data and search for that specific flight to find the list of aircraft which flew with the callsign and if you select any one of the planes, you can find out the flight history of that plane for the past few months. You could also search flightaware.com/ for flight history too.