Hi Dear,
In respect of your Investment in NSC, you will get deduction u/s. 80C upto max. limit of Rs. 1,00,000/-. There is no 1st or 2nd year provision in respect of this.
In case of Interest earned on NSC, it is taxable under the head "Income from Other Sources". It is advisable to include this Interest in your Income on yearly basis instaed of on maturity.
If you don't declare this interest in your Income, then at the time of maturity of NSC you will have to pay the tax on benefit received (i.e. the difference between Amount Invested and Amount received on Maturity). However, if you declare interest as part of your Income regularly, then don't worry about the taxability of Maturity Value since it will not be taxable.