It lasts until it blows ....
There is no need to replace it regularily. It will last for the lifetime of your car if no fault in the cars electric system occurs.
If the car is a Diesel there is 30 amp open fuse on the firewall
Depends on what that fuse protects. Highly unlikely you can drive this car with a 100 amp fuse missing but possible.
No, you could overload the wiring and start a fire.
The number on a car fuse refers to the Ampage of that fuse , each electrical component on any car has its own or shared fuse with a certain Amp rating, they are normally colour coded too and are to be replaced with one of the same Amp rating for protection.
It should work with a 20 amp, just not as long. Wipers use a fair amount of current so the factory puts a 30 amp in. Perhaps that particular 20 amp is bad or it blew as soon as you turned the wipers on.
The starter is failing.
Any auto parts store.
20 amp circuit breaker
under the hood of car on passenger side and it is a 20 amp yellow fuse
( # 17 ) is a 30 amp fuse for the cigarette lighter on a 1997 Lincoln Town Car
Back of car - fuse panel next to battery - fuse number 18 - 20 AMP.
Use a small screwdriver to pry upwards . these fuses are very hard to remove sometimes.