When is a sale and purchase transaction of an NFT completed?

A sale and purchase transaction of an NFT is typically considered complete once the buyer has paid for the NFT and the seller has transferred ownership of the NFT to the buyer. This transfer of ownership is typically done through a blockchain platform or marketplace that supports the buying and selling of NFTs. Once the transaction is complete, the buyer becomes the owner of the NFT and has the right to hold or sell it as they see fit.

Considering that the transfer/registration is the closest to the definition of "tradition"
presented in articles 1.226 and 1.267 of the Brazilian Civil Code, the purchase and sale of a NFT
is completed when the registration on the blockchain is completed, in the moment the nodes
validate it and the transaction is successfully made.

Not as of now.

Subject to the stipulations of the contract or sale of goods terms, as soon as the
buyer pays the price of the offered NFT, a consideration arises in law, and the
transaction is completed as soon as the delivery of the item is made.

In general, under Polish law, a contract is considered to be concluded at the moment of mutual consent of the parties, which means that the transaction is completed when both the buyer and the seller agree on the terms of the sale, and the payment is made by the buyer and the NFT is delivered to the buyer. However, when it comes to NFTs, the buying and selling process can vary depending on the platform or marketplace used and the specific terms and conditions of the NFT. In some cases, the NFT may be transferred through a smart contract, and the transaction is considered complete when the smart contract is executed. It’s important for the purchaser to carefully read and understand the terms and conditions of the NFT, including any information provided by the creator about the buying and selling process, before making a purchase decision.