If Gandhi is reborn, will he become a leader like before? If Newton is reborn, will he be able to discover or innovate as many as he did?

The answer is "NO". Gandhi & Newton are successful if they are reborn only if their life is repeated as it is, that includes time, people around them, environment and many other factors. There are many aspects or incidents in life, which are attributed to an individual behaviour or success, those aspects unleashes or uncovers many great qualities of an individual. You just learn from the biographies of the great leaders to get inspired and keep doing the right thing.