Taxability of salary earned outside india

Dear Team,

Please guide me in following case:-

Facts of the case are

Mr. X leaves india in November for 2 years employment in USA. He will be geting salary in USD and tax will be deducted by US company there itself. My query is:-

1. What exchange rate to be applied for included his salary earned in USD while filing income tax return for the year in which he left india?

2. Whether he will be entitled to tax benefit for tax deducted in USA while calculating tax liability for the year in which he left india?

3. If salary received in USD for next year not transferred to his NRE/NRO account, whether the said salary is taxable in india? if yes, tha at what point of time i.e. in the year it is earned or upon returning after two years

Thanks in advance

Manish