At speeds above ~150 km/h, even on a well-organized highway, you won’t be able to control your surroundings and have to rely on sheer luck to survive, unless you’re a professional race pilot on an empty road. Also, unless the car is equipped with special gear for improved road grip, it will become uncontrollable because it will literally start to hover a little.
sorry but no. maybe i am biased since my sole experience is driving the german autobahn, but i drive well beyond 200km/h on a regular basis, which i consider travel speed when the road is not too crowded. cars that could go faster than 250km/h are usually limited to 250km/h. traveling at that speed is loud and a bit stressful, since the difference between you and other cars traveling at lower speeds becomes too high. they will not see you coming before switching lanes and braking distances are very high. but cars dont randomly switch lanes unless tying to pass others cars and you can predict these situations and slow down.
you will not hover, you can control your car normally and the only required luck is to not have others actively try to kill themselfes. you dont need to be a professional race pilot and dont need special gear (of course cars can easily be underequipped for these speeds, but you dont need special gears.
do you mean speeds above 250km/h or speeds above 150mp/h? if that was just a typo i would argue a lot less because those speeds stop being fun to drive, but are also accessible for normal drivers with normal street cars (with enough power of course, but you see plenty of those cards on the average parking lot in front of any supermarket)
probably not, unless you add certain services back onto your phone. currently, gemini needs the google workspace to do anything, even something like setting a timer or reminder. i obviously dont know what change they make with that announcement, but i dont think they would offer such a feature without sucking the user deep into the google service world.