The superlative degree of 'Far' is :

Right Answer: Farthest

The adjective 'far' has two sets of degrees in modern English. When distance is meant, the forms are far – farther – farthest, and when order, extent or additional amount is meant, the forms are far – further – furthest. Therefore the superlative degree of 'far' is 'farthest'. 'Farther' is only the comparative form, while 'most far' and 'most farther' are not accepted, because adjectives that already have irregular comparative and superlative forms are never compared again with 'more' or 'most'. Hence option (2) is correct.