https://thegraph.com/docs/en/developing/creating-a-subgraph/#data-source-templates

The Graph supports starting a dynamically instantiated data source from a block earlier than the current block?
The dynamic data source instantiated from a template begins processing events from the block where the .create() function was called. Is this correct?

What I wanna do is not to create a collection but to add an existing collection to the factory. In this case, I simply add a function which emits same events as the collection is created to the factory contract. But mapping function of factory contract works but template mapping function doesn’t detect the minting events.

>Solution :

Yes. It starts processing events from the block where the .create() function was called.

You can review Part 9 at https://thegraph.academy/developers/defining-a-subgraph/

What you ran into is incapability to process the historical data.
Currently, I am not sure if there is a way to fetch past events without reading the current state of the contract?
see this screenshot