thanks Christopher Solomon.
When I check in debug mode that fields indexes are having 1 not 0. So I started with 1 itself. Any how both the way it's worked.
What you said is correct indexes are not string. I just do trail and error way in INITIALIZATION method since it's not worked when I pass as integer. So I made it as value in quotes.
But it's worked in both the ways in DO_OPERATIONS method. No issues.
For dynamic I already made in same way what you have mentioned the logic.
thing I missed to make it as default value for those fields in generic service.