What am I religiously entitled to claim in this situation: the car’s price and the cost of ownership transfer? And what is the religious ruling on the duration of the option?

The buyer has the right to revoke the sale and return the defective car to the seller, recovering the full price, or to keep it and receive compensation for the reduction in price due to the defect, if the defect existed before the purchase and the buyer did not consent to it. The cost of transferring ownership is treated like the cost of writing the contract, and the buyer does not have the right to recover what he paid for it from the seller, because the burden of returning a defective item falls on the buyer. The option of defect does not have a specific duration; whenever the buyer's right to return due to a pre-existing defect is established, he may exercise this right at any time.