Hazard lights should always work as long as the 12V battery is good and those lights function. The switch for the hazard lights is above the rear view mirror, Tesla was forced to make this a physical switch, the rules. If that is not working then schedule an apt. That is supposed to work no matter what, in case of disabled vehicle on side of road.
As for driving, the car is supposed to still be driveable even if the computer does a reboot. If you are uncomfortable about driving should that happen, just pull over and wait. The computer is an add-on, it should not interfere with your ability to still drive the car manually. Of course you will not have navigation, etc. while it is rebooting. If a computer reboot while driving would cause the car to be no longer driveable then there is a much bigger problem and we would not have these rolling computers on our roads.