creating checkbox dynamically based on FDM in AEM 6.4

Hi,

We are trying to create checkboxes dynamically based on a service in AEM forms 6.4. I know there is an option available in 6.5 but not able to achieve it in 6.4. I tried one of the options mentioned here but no luck

https://experienceleaguecommunities.adobe.com/t5/adobe-experience-manager/dropdown-in-aem-forms-6-3-using-data-integration-i-e-form-data/m-p/264722

and the other option we tried is to invoke the service of FDM into checkbox initialize event like in the screenshot but no luck there too

Appreciate any ideas, thanks!