The date you are issued an immigrant visa is irrelevant. The date you entered the U.S. is controlling. Since you were 19 at the time you entered the U.S. you did not obtain U.S. citizenship under the Child Citizenship Act.
Generally speaking, shoplifting is a misdemeanor and while a crime involving moral turpitude, may be subject to the petty offense exception and thereby not render you inadmissible. It also appears that you be eligible for other forms of relief from removal.
Consult with an experienced immigration attorney who can review the facts of your case and advise you how best to proceed.
While this answer is provided by a Florida Bar Certified Expert in Immigration and Nationality Law, it is for general information purposes only and an attorney/client relationship is neither intended nor created. You should seek out qualified counsel to review your case and provide you with advice specific to your situation. Call +1-561-478-5353 to schedule a consultation with Mr. Devore.
Under current citizenship laws, you would not derive citizenship on these facts, because you would have had to have been admitted to the U.S. as a lawful permanent resident before you turned 18. However, you do not say how old you are now, and citizenship laws have changed over the years. The governing law may be different based on the date of your birth. Also, you may have other options in removal court. The important thing right now is that you should consult a qualified immigration attorney on how best to proceed. Your future and ability to remain here in the U.S. are too important for you not to seek the services of a qualified immigration attorney and there are plenty of good ones here in Florida who can help you. Best of luck.