"Best" is a subjective term that will be based on your pocketbook and what you are using the rifle for.
100 meters.
The Type 97 Sniper Rifle is a Japanese bolt-action rifle using 308 Federal 175 grain bullet.
Yes
308 Rifle can hit a target over 300 yards away. The military used them as sniper rifles and they r more accurate than a .223
175-250 dollars.
Unless you're an optician, you can't. The US military has standardized on Leupold scopes for its snipers, so if you want a sniper scope, go to a good gun store and buy the Leupold scope you like best. Then, go to a gunsmith familiar with high-accuracy rifles with your bolt-action rifle (Remington Model 700 is a very good gun and .308 is the caliber I would choose) and have all these things done to it: fit the stock to you, glass-bed the stock (this makes the stock fit against the barrel nicely and cuts down on vibration), polish the bolt, have the headspace adjusted, then mount the scope. And THEN buy about twenty boxes of match-grade ammo and learn how to shoot. The scope is just part of what makes a rifle a sniper rifle; it's a system including the rifle, optics, ammunition and shooter.
Each will perform as intended within its range limitations.
No such rifle. The Lee Enfield was made in caliber .303 British, not .308. The closest thing would be the Ishapore 2A or 2A1 rifle, made in caliber 7.62 NATO. While similar the .308 Winchester, it is not the same, and .308 should not be fired in a 7.62 NATO rifle. The Lee Enfield "sniper" rifle in .303, if original and complete (and not an aftermarket conversion) may sell for around $1500, depending on condition and accesories. There are many fakes on the market- be sure of what you are buying.
It fires a 7.62x51mm NATO bullet, which is similar to a .308 Winchester.
The cartridge itself is. It has a flatter trajectory than the .308. As for the rifle itself, it all depends on the tolerances and build quality.
4x, 1-4x, 3x9 are all candidates