In Career mode, you start off with the Junior WRC cars and work your way up though to WRC1. The seasons become longer as you go through the classes. A season may consist of many rallies, and each rally is comprised of 6 races, with a chance to repair your car and tweak your car set-up after 2 race intervals. The races are standard rally, so its a race against time on a point-to-point track. Your times across the tracks are added together to calculate your overall finish in that rally.
As you win, you gain reputation which allows you to sign with higher prestigious teams. Depending on your reputation, you may have the option of skipping classes so you don't actually have to go from Junior to WRC3, you could jump to WRC2 instead.
There are 16 countries with various stages within which can take place in various times of day. There's plenty of surfaces to race on across the countries, so you will travel on road, gravel, mud and snow.
In WRC1, the rally is across the 16 countries which takes a long time to complete. Your progress is saved after each race, so you can do it over many sessions; but it is still a gruelling task.
If you make a mistake during the race, you can use the Rewind feature. This feature can be disabled, or limited as you see fit. I felt the game was a bit too eager to reset your car when you drove off the track. On several occasions, I drove off the track, decided to rewind, then the game decided to reset my car anyway. So this is a bug to bear in mind.
Another annoyance is that when you get the opportunity to repair your vehicle, Start Race is selected by default which means you can end up skipping the chance if you aren't careful. It seems strange not to take you to the repair screen by default.
It's an old game so the graphics looks dated. There's no in-game graphics settings either. You have a choice of resolutions, V-Sync and Anti-aliasing on the configuration launcher; but that's it. The graphics on my computer suffered from some "salt and pepper" noise. The game requires some Windows Media Player DLLs, so I had to add these DLLs manually on my European Windows 10 PC since that software doesn't come as standard. I couldn't get the video footage to work though, you just get black screens.
In summary, I think WRC4 is a decent rally game but is a bit dated. It's fine to play, but there's better modern games available to play instead.