In magento1 I want to create a Coupon & apply that coupon when only specific brand product is added to cart, if any other brand product is applied then the coupon code should be automatically removed or should not apply.
You can create a new product attribute as a brand and assign value to products using mass action. After that Make sure you set value Yes in the dropdown "Use for Promo Rule Conditions" for the brand attribute.
Now you can able to see the brand attribute option in the action section while you creating a new promo code.
Hope it will solve your problem