Ans: you can withdraw the entire amount but it will be taxable depends on the number of years you have been working for

Ans: The lock in period for PPF is 15years now so you can withdraw it before 20 years as well. You can withdraw a sum equal to the sum given by banks on their investments for day to day expenses if you have retired. If you have not retired and have an active income then keep the investments for them to grow as you technically don't need the money. You can do diversification of this investment and keep it invested in a couple of assets like PPF , equity mutual funds , debt mutual funds , etc.