My dad had a friend who used to do this, although not at freeway speeds. He’d go about 30 or 40 miles an hour and throw it into reverse. The car would slow down rapidly and eventually start backing up.
And now the rest of the story: This was my dad’s friend and this happened a long time ago. The reason the guy would do this was to show off that he had one of those new-fangled “automatic” transmissions in his car. And he had to get a new transmission after a few months of this showing off.
Theoretically, you could do the same thing at freeway speeds with a modern transmission since (again, theoretically) there is a fluid coupling between the transmission and the drive shaft. But today’s transmissions are a lot more sophisticated than they were in the forties. That fluid coupling (which is still there, otherwise you’d have to use a clutch when you were stopped) is assisted by other equipment. Most new cars have a means of creating a mechanical coupling in top gear. (This is slightly more efficient and efficiency is very important in the auto industry.)
With a mechanical connection and a sudden shift into reverse you’d have: 1) the engine going madly one direction, 2) the wheels, etc., going madly in the same direction and 3) Hi Opal! – no I mean 3) the transmission wanting to go madly in the other direction. Something would break.
Even if there were a fluid coupling the fluid would (at least) get extremely hot. It would probably break down, cease to lubricate and again, something would sieze, followed immediately by something breaking.
Only in the rare case that everything survived the sudden shift in direction would the car do as described above – slow down and then reverse. And even then it might slow more quickly than the tires (or the driver) could handle.
My advice – don’t do this. However, if you do do this by all means take pictures. Your family will want them when they receive your Darwin award.