No no, before you even pull the clutch up it makes a massive crunchy noise and won't let you pull the gear stick fully in to the reverse position. You could probably make the gearbox explode if you pulled the gear lever really hard.

I know this because reverse on my current car is where 6th gear was on my previous car.

You would be lucky to get it into reverse because its usually a straight cut gear, but i expect you could downshift to 1st from 5th at 70mph with a good enough shove. Then something on the car is going to be upset with you.
Why..?

Because no one is driving the cars you see flip on a film. They are on a cable.

Also, it wouldn't be predictable enough

I saw a programme once where some physicists (of some description) were posed the question of putting a car into reverse at 70mph. They came to the conclusion (using science and stuff) that the energy released would act like a bomb and blow the car in half with a great deal of violence. That said, I once dropped a Corsa into second at 90mph. I should point out that the move was deliberate on my part, since I needed the engine braking to assist the actual brakes in allowing me to avoid rear ending the bloke in front. It worked, and if it damaged the car, I certainly didn't notice.

As to the OP's question, I'm sure it depends upon the car, some may dig in and roll, some may even rip a tyre from the rim. Others would likely slide either understeer or oversteer (the latter would certainly be the case in a Focus). Too many variables really, but an interesting question. Maybe one of the childrens' science programmes (that thing with Richard Hammond, perhaps) will follow it up if you write in?

Simon.

Surely the car, vehicle height, tyre width and speed would make all the different. OP, can you be more specific. Also depends if you turn left or right!

Pish.

Depends on the car and the throttle movement too. I'd imagine if you had a wide enough stretch of tarmac (maybe 300 yards wide) and you did this in an Integra Type R with a constant throttle then it would understeer a bit initially and then gain grip eventually and start turning hard. If you backed off the throttle at the same time, I assume you'd provoke a spin.

Was this sparked by a pub debate?

My Suzuki Jimny with a 2 inch suspension lift would just fall over. It doesn't need motorway speeds either tbh.

Getting to full lock quickly would not be easy. The first big bite of steering input would use all the slip angle up and as the car rolled it then all depends on the chassis tuning whether you spin or go forwards or backwards into the barrier or off the edge od the hard shoulder. At this point you are a passenger. Getting control back after you did rhis would need more knowledge and skill than the average driver has, and need to be done really quickly. You would have to get the front wheels turning and with a linear slip angle variation along the contact patch again in less than a second I would expect. Then you would have to catch the car as the springs unwound. Flip or slide depends on the car, my thoughts were for a b segment eurobox, clearly s 4x4 would be more likely to flip. Cars like my MGs only kill you by going upside down if you slide into a kerb at speed, although its been done.

Cable??? Stunt men do drive these flipping cars for realism in films and they tend to use gas rams under the car or pipe ramps if flipping after hitting something.