Relief u/s 89(1)

Hello everyone!

Can anyone help me out with this?

Facts:

1. My friend has received arrear salary pertaining to two previous years.

2.In one of the previous year, he actually did not recieve any salary, he received only stipend.

3.In both the previous years his income was below basic exemption limit and so he has not filed his returns.(I am going to file my first return)

My Doubts:

1.Can I claim relief even when I have not filed my returns in those respective  years?

2.How do I calculate Total Income for the year in which he was receiving stipend?

Thanks in Advance!