You are not committing a crime by driving the car.
However-the proper thing to do would be to return the car-up to you and mother unless she can make another deal.
The answer given does not imply that an attorney-client relationship has been established and your best course of action is to have legal representation in this matter.
If you are going to drive the car, buy insurance for it. Do not drive it without insurance. If you want to keep the car, contact the finance company and see if you can resume making payments. They will not allow you to transfer title unless you payoff the car. You could apply for a car loan. The executor could sign off on the title. The old lien would be paid off. Then you would have title in your name, plus payments to make.
No lawyer-client relationship exists. This answer is intended for discussion purposes only. You must obtain legal advice from your own attorney.
You can drive it until estate no longer owns it so long as you have permission of executor. Unless Will has been filed for probate and your mother appointed as executor and filed her oath, she has no power to act. Assuming your mother has qualified as executor, there is a claim process that needs to be followed by her.
You cannot insure it as you do not have an insurable interest. Unless it is titled to you, the estate must be the named insured.
Exchange of information through Avvo's Questions forum does not establish an attorney-client relationship with me. That relationship is established only by individual consultation and execution of a written agreement for legal services. See http://zgourides.com for more information.
It sounds as if the title has never changed. Driving it in its present titled state may put the estate at risk for liability if the driver is found at fault in the accident.
The answer to your question on this forum does not constitute an attorney-client relationship. You are advised to seek counsel for a complete and thorough assessment of your legal issue.