How Replace Price By Old Price In Cart?

I have a request like this:
Instead of Price being added to the cart when clicking the add_to_cart button, we will add the following condition:
- If Old_Price> Price, then Old_Price is added to the cart.
- If Old_Price <Price or Old_Price is null, then Price is added to the cart.
And further processing:
- If the logged-in user belongs to group A, the minimum required quantity is 10.
- If the logged-in user belongs to group B, then the minimum required quantity is 1.
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Please help!!!

I am afraid, code changes are required for both cases