What’s the difference between the right of withdrawal and open purchase?

It is only when you have signed a contract remotely (via the internet or phone), through home sales, or at another temporary sales location that you have the right of withdrawal according to law.

You therefore do not have the right of withdrawal if you entered into the contract in a store. But if you and the seller have agreed on an open purchase, you can refer to that if you want to withdraw from the contract.