It seems that you're using an outdated browser. Some things may not work as they should (or don't work at all).
We suggest you upgrade newer and better browser like: Chrome, Firefox, Internet Explorer or Opera

×
1. Silver Fletcher
If you missed it in 11th mission Visiting Rich People, either you didn't know that's the time you can unlock it or had trouble escaping with it without enemies blowing it up, fear not, you can still unlock it.
Go into Free Ride mode, go to the lighthouse, there you will see the car. Drive it to Salieri's bar. I don't know all the locations you can put it, but I do know that 500m from this location and tipped on the side is not good enough. On second try I parked it in front of red doors that lead to the parking lot behind the bar in story and in FRE. It should probably also work if you park it in front of bar's door.
Then save the game at the bar door and you will unlock it in Free Ride.

2. Caesar 8C 2300 Racing
Apparently after some patch which current GOG version certainly has, there's a bug where you don't unlock it by normal way completing the FRE mission Race Car Exchange.
Interesting fact is that in FRE you can drive back to the house both Caesar 8C Mostro and Caesar 8C 2300 Racing, but not the other 2 race cars, Brubaker 4WD and Carrozella C-Otto 4WD.
Anyway, to unlock this car, load your Free Ride Extreme home save game where you already finished this mission. Drive to the old prison on Central Island and go into the red race car.
Drive it to Salieri's Bar, then go to the parking lot behind it and park the car under the wooden roof where Ralphy had new cars for you before story missions. Front first will be best as you go in the car on the right side. First I made a mistake reversing it flat against the wall and I couldn't get back into the car to drive it back to my home parking lot.
Then drive home with another car and save game at home and you will unlock it in Free Ride.
Optionally in FRE you can drive back for the car, if you like to keep a collection at your home.

3. Bolt-Thrower
If you come to a bug in FRE mission Invisible Man, either the train never comes or he gets scared of Speedy Gonzales lying dead on Giuliano Bridge and doesn't go off the train, you can still unlock this car in Free Ride.
If everything is normal, trains come every minute or so. For me it bugged out when I've done the mission where you have to exchange the 3 racing cars.
Simply start a new Free Ride Extreme and go to this mission first, then there will be no bugs. Mission is located in New Ark in front of Morello's Lounge Bar.
There's a few tricks to this mission, once you're at the train station for the first time, you can stay there. Invisible man will go down and hide behind some beam, then he will come back. He will enter the train through the second door from the front of the train. Once you're off the train at the next station, he goes across the road, then he runs right into the alley, on the right side of two gardens and when he reaches the road, he turns left and stops at the door of the first building, that's where you unlock the car.

There's also a way to spawn the car in Free Ride Extreme without doing this mission. You go to the West Marshall Bridge, turn east, go on the left side of the bridge and shoot at the middle window of the bridge tower. Shoot at the upper half of the window or in the middle of the window (everything but the lower half), so that the screen flashes black once.
Then go before the East Marshall Bridge facing east, car is on the left side of the bridge at the end of the alley.
With this car and doing the same routine as with Caesar 8C 2300 Racing, you CAN'T UNLOCK the car in Free Ride, you MUST COMPLETE the Invisible Man mission.

Most other Prototype cars should not be a problem to obtain.
For Exploding Celeste and Bridge Bombing Zeppelin you have to limit the FPS to 15-20, I used 15. I did that in RivaTuner Statistics Server which comes with MSI Afterburner. In Bridge Bombing Zeppelin I drove on the right side, even on the pavement towards the end.

I'm quite sure in the end you will be left with two missions that require more than 5 tries opposed to other missions - Airplane Chase and Speed Explosive Truck.
In Airplane Chase you must know the route the plane is taking, it goes over Giuliano Bridge, then take a shortcut to Central Island Tunnel, just right after the bridge, left into the alley and right on the main road again. After that it's basically just straight if you cut the left and right corner through the grass.
In Speed Explosive Truck the path you take is very important. Go straight past East Marshall Bridge, take a left turn cutting through the pavement, then take a wide right turn on a double street, then through Central Island Tunnel, at the end take a wide left turn over the grass and between all the train track pillars, again at the end take a wide left turn close to the wall, at the end take a wide right turn cutting through the pavement, then it's straight to the finish.
This mission requires a lot of luck, I needed 20 tries to finish it. You're dependent on traffic position a lot, sometimes it's just not possible to go through. Or someone cuts in from the left, you have to turn right to avoid, then there's a right turn and you're positioned too much to the right, you go through the turn and end up in the car on the opposite lane.

With the help of this guide and others throughout the internet you can get all the 19+1 cars in Free Ride Extreme even if the game puts all the possible bugs in your way.
You can also unlock all the cars, all 4 race cars and all 19 prototypes in Free Ride.
Post edited September 23, 2020 by robip85
I can confirm the bug with Caesar 8C 2300 Racing - it doesn't unlock. Following your post, I managed to unlock it, thanks!

You can actually drive back the Brubaker 4WD back to your house - stay in the car when the mission ends. If you load the save, you should be able to enter and exit the car. Unfortunately, once you save the game and load it, you'll lose the ability to drive it again.