The cooling off period always applies only if the product is returned in the original condition. An easy way to keep this in mind is to return the product in a condition you would consider buying it yourself.
You can try on, touch & feel your product but it has to be clean and unused when it is sent back. However there are special rules for hygiene products like skin & hair care, underwear etc and for food & drinks. Those are often packed and sealed. The product can only be returned if the seal is not opened or damaged.
Please note that products on final sale are not eligible for free returns.