Dear Mayank,
As far as my knowledge goes for WC Policy, the insurance company needs these details for WC Policy:
1. Number of Workers to be covered.
2. WC insurance coverage period: From To.
3. Wages of the workers during the coverage period.
4. Nature of job in which the workers are to be engaged or Work order in the case of contract labor.
5. Nature of job in respect of risk involved (for premium amount).
I do not have any idea whether 'Age' is a factor in the case of WC Insurance or not, but generally, I have never seen any policy where the age of the workers is mentioned. So, I think in your case, if the number of workers covered under WC Policy is 20 and each shift has 20 workers, there is no risk involved as far as payment of compensation by the insurance company in case of an accident is concerned. But make sure that at any shift, the number of workers should not exceed 20. However, if at any time you will be required to engage more than 20, do not keep any documentary proof of that.
Regards,
Jawed Alam