Can one go to jail for not filing returns and can he receive refunds when filing delinquent returns?

Let me answer your last question first.  You will not go to jail for not filing under the situation you have described.  You only go to jail for a criminal offense, such as fraudulently evading your tax obligation.  If you have been suffering from depression and were treated by a doctor, that certainly would not constitute tax evasion.  The IRS will be glad to see you make things right and begin paying your taxes.  Be sure you file your 2020 return on time.  As to your first question, even with penalties and interest, you might still be able to get a part of any refund but only if the due date was less then 3 years prior to the date you file.  Thus, you can get a refund for 2017 and later but not for years prior. However, those returns must be filed by April 15, 2021 (even though the deadline for filing your 2020 return has been extended to May 17).  Any refunds to which you would have otherwise been entitled for earlier years go to the general US treasury.  We will be happy to file those returns for you. After the returns are filed, we can determine how much you owe and make arrangements to satisfy the debt in one of several ways.