No.
Yes
When fired from a .303 rifle, it can travel ABOUT 2.5 miles.
The .303 Enfield rifle can fire a bullet about 2 to 2.5 miles- but is not accurate beyond about 600 meters.
Assuming you mean a rifle such as the SMLE, the cartridge used in the .303 Enfield, also called .303 British. See the link below for information on this ammo. However, if you are not certain (some military surplus rifles were rebarreled into other calibers) have a gunsmith take a look at it.
303 was the .303 inch diameter bullet that was fired by the Short Magazine Lee Enfield- or SMLE. Standard rifle of the British military from 1907 to the1960s, and still in limited use today.
No. The L1A1 Self Loading rifle in in caliber 7.62 x51 mm (7.62 NATO) fires a rimless cartridge with a .308 bullet. The .303 Enfield cartridge is a different shape, has a rim, and fires a .311 bullet. If you compare the two cartridges, totally different in shape.
Bren gun, Lewis gun, SMLE rifle
The typical rifle bullet was .303 inch caliber. The same round was used in most of the light machine guns.
2441 feet per second when fired from the British SMLE rifle. Velocity will vary when fired from rifles with a longer or shorter barrel.
No. Two totally different cartridges, and it is HIGHLY unsafe to attempt it. No.
No. You wouldn't even be able to get the .303 to chamber in a .30-30 rifle. They're two very different cartridges, in no way interchangeable with each other, and this should not be attempted.