I need to used multiple delivery templates in Single delivery through script based on certain segmented criteria and intializing that segment criteria in JS Activity just before the delivery but when I tried to use that through script just for one delivery template then It moved the delivery template to finished state but I need to use same delivery template multiple times and need to maintain Delivery transaction details for every delivery.
As far as i know, a delivery activity can only use one delivery template for each iteration (in other words you can't have your entire audience connected to one delivery activity, and then generate multiple deliveries from different delivery templates)
You can dynamically change the delivery template that is used by the delivery activity, for each iteration, but as mentioned above, only one delivery template can be used each time.
I would suggest using personalisation blocks or splitting your audience into different subsets and using multiple delivery activities.
I don't remember seeing this and I doubt it is possible. I believe you need to make your template more dynamic to meet your needs or you need to split the universe into multiple segments before directing each sub-universe into the proper delivery activity node (which is helpful for reporting).
Can you provide a use case why you need to use multiple delivery templates in the same delivery? I can't say as I've ever seen this technique deployed successfully before and am not sure if it's supported by the application.