Do you want to return the car because they didn't get financing? If so, you have to refer to the written purchaes contract to see what it says about the dealer not being able to get financing within 10 days. You may be required to return the car and pay them for the reasonable cost of using the car for 3 months. The dealer has been waiving whatever rights they've had since day 11, but could assert their rights to cancel the contract, so they must think they can find a bank to finance this sale.
See a lawyer to review the contract and advise you of your specific rights and responsibilities.
Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.