one question when filing greencard for parent

I am a U.S.Citizen and will help my parent obtain Greencard. For I-864 form, I need to request my tax return receipt from IRS. Because I just moved lately,I need to mail 4506-T "Request for Transcript of Tax Return" to obtain my tax return proof. In 4506-T, we can request Return Transcript, Account Transcript, Record Account, etc.

So, "Return Transcript" is enough, right?

Also, How many previous years are needed? four years?

Thanks a lot.