Share your form, need to look into the form layout and script

this.resolveNode("headersubform.childsubform.child2subform[" + sprec +"]." + "DDS[" + i + "]").ui.oneOfChild.border.fill.color.value = "255, 255, 153";

For DDS[i], use it like the same you are using [" + sprec + "].". It should work then.

I think the Document of record can be an option for this.   https://experienceleague.adobe.com/docs/experience-manager-65/content/forms/adaptive-forms-advanced-authoring/generate-document-of-record-for-non-xfa-based-adaptive-forms.html?lang=en  

For the first question: do you mean to create multiple copies of the first page at design time or after rendering the form? At design time you can add new subforms and fields to design the form or copy/paste the existing component available on the form. or Use the instance manager to repeat the subf...

For GDS, you must make sure that the directory is not located at the root of the drive but is located in a subdirectory. For example, the directory should be D:\GDS and not simply D:\.   Only the administrator account that is used to run the application server should have read/write access to the GD...

columnWidths property helps to set the width of the column dynamically.   https://help.adobe.com/en_US/livecycle/10.0/DesignerScriptingRef/WS92d06802c76abadb-3e14850712a151d270d-781a.html

If there are multiple selections for the sub-dropdown for some value in the first dropdown, then you need to take the sub-dropdown in the form. You can place the sub-dropdown in place of the text field you are putting in the form. You can have both dropdowns visible for the selection, I don't unders...

The below link has your answer:  https://experienceleague.adobe.com/docs/experience-manager-65/content/sites/administering/introduction/tc-msconf.html?lang=en    

Refer to the below to give proper privileges and roles for your user group to work with the template and forms. https://docs.mktossl.com/docs/experience-manager-65/content/forms/manage-administer-aem-forms/forms-groups-privileges-tasks.html?lang=en