(i) False. The smallest two-digit natural number is 10, and the cube of 10 is 1000 which has 4 digits in it.
(ii) False. The largest two-digit natural number is 99, and the cube of 99 is 970299 which has 6 digits in it. Therefore, the cube of any two-digit number cannot have 7 or more digits in it.
(iii)True, as the cube of 1 and 2 are 1 and 8 respectively.