In the number 819257643, digits are processed as follows: If a digit is less than 5, replace it with (digit × 2). Otherwise, replace it with (digit - 3). What is the difference between the highest and lowest unique digits in the final number?

The 'Drain of Wealth' theory was propounded by which Indian nationalist leader?

Which event is considered the turning point in Mahatma Gandhi's leadership in the Indian independence movement?

Which African leader is known for his non-violent opposition to colonial rule?