To clarify, in your example you want to produce product or productA and ProductB?

I don't want to Produce anything here. My main product is Product and that I am purchasing from the another supplier so I want to unbuild it. What I have tried I have created a BOM as a kit (product Main Product- Component as a Product A and B) but when I am trying to unbuid it and it does not work.

Yes, you can’t unbuild what was not manufactured.
If your intention is to get Product A and Product B from your main product, then create a BoM for Product A, with Product B as by-product and the main product as component.
In essence you are creating/ producing Product A and Product B by consuming main product.
Hope this clarifies.

No, It is not clarifying. Please give me the proper example and bom in the sense of what manufacture or kit?

It is manufacturing
Create BoM for product A (not for main product), have Product B as by-product and main product as the component.

Thanks for your help but it does not work for the component or as per your example the main product stock increasing and component stock decreases the ultimate thing is it does not work in these manner not the ideal solution in terms of inventory and accounting.

Might be some custom solution have to find.

thanks

Not sure if I completely understand your comment. Clarifying here as your comment refers my example:

In what is being suggested the main product is purchased so stock increases on receipt and since it is a component in the BoM, it would be consumed (decreased) when Product A and Product B stock increase.