Aniket,
Based on how the classification datasource is configured, it should have the ability to inherit the delta property of the base datasource. In this case since 2LIS_13_VAITM is delta capable, your generated classification datasource should also be.
I worked on this 10 years ago so my knowledge is admittedly rusty, but in general to answer your questions:
1 - It can be linked to transaction data as well (for example variants of an item in different sales order wouldn't link to the product/material as master data, but would be linked to the sales order document). Depends on what information from classification you are pulling.
2 - As mentioned above, delta should be feasible in your case.
Cheers,