If the lock in period of 15 years is over in your case then you can withdraw the entire amount however if the lock in period is still subsisting, in that case, pre-mature withdrawals can be made from the end of the sixth financial year from when the commenced. The maximum amount that can be withdrawn pre-maturely is equal to 50% of the amount that stood in the account at the end of 4th year preceding the year in which the amount is withdrawn or the end of the preceding year whichever is lower.
you will be able to earn interest on the PPF if you have chosen the option of extending the PPF beyond 15 years without making any further contribution. in that case, after the maturity period is over, if within one year no action is taken by the subscriber then any amount can be withdrawn however only one withdrawal is permitted in a financial year. rest of the amount will earn interest.