Is the seller obligated to ensure the delivery of the land to the buyer if its documents and accreditations are incomplete, with the buyer's knowledge of this and upon full payment of the price?

For the sale of land whose paperwork is not yet complete to be valid, you must be able to deliver it to the buyer in such a way that he can benefit from it and dispose of it as an owner. Otherwise, the sale is void, and the buyer is entitled to a refund of the price.

The ability to deliver at the time of contracting is a fundamental condition, by the agreement of jurists, even if the item is owned and existing. However, if the deficiency is merely a defect in the paperwork that does not prevent delivery, and the buyer was aware of it and accepted it, then the sale is valid.