No. Only 18 inch tires fit an 18 inch rim.
Yes there was a factory option for 17 inch wheels
Yes.
yes
Bikes with 18-inch wheels are lighter, more maneuverable, and provide better acceleration compared to larger wheels. They are also easier to transport and store, making them ideal for commuting or recreational use.
The 1995 Pontiac Firebird can be fitted with 18x8-inch wheels granted they are designed for this application. A tire size that will work on these wheels are 275/40/18.
Stock it comes with 18 inch on the GT
27
18 inch back not sure on front
Cycling enthusiasts may prefer bikes with 18-inch wheels for their agility, quick acceleration, and maneuverability. These smaller wheels can provide a more responsive and nimble ride, making it easier to navigate tight corners and obstacles. Additionally, bikes with 18-inch wheels are often lighter and more compact, making them easier to transport and store.
Keep the diameter of the wheel/tire the same with the 17" wheels as you were running with the 18" setup. That will require that you install a set of tires on the 17" wheels that have a larger diameter than the tires now currently on the vehicle. w www.tirerack.com is a good place to find out exactly what size tire to buy.
The 18 inch wheels have very large surface area which reduces the pressure that the car exerts on the road.