How can a former deportee apply for EB-5?

In spite of the fact that your case was over 20 years ago, it is advisable to contact an immigration attorney to check about possible outstanding issues that may make you inadmissible. If necessary the attorney may pursue a waiver on your behalf. This should be done and resolved before proceeding into a comprehensive pursuit of an EB-5 petition.

False claim to U.S. citizenship is not waivable and you are barred forever. There are only a few exceptions for minors.

Your use of a fraudulent document could affect your application for an immigrant visa. The U.S. consular officer has discretion on whether to grant an immigrant visa. If this occurred more than twenty years ago and you had a clean record since this event, then the U.S. consular officer may grant the immigrant visa.

A false claim to U.S. citizenship is permanently fatal for permanent residency unless you were a minor.

If you made a false claim to U.S. citizenship after 1996, there is no waiver available and you remain inadmissible to the United States as an immigrant regardless of the passage of time. You may be eligible for a nonimmigrant waiver and possible could obtain an E-2 treaty investor visa, not an EB-5 green card, but you should have an immigration attorney review all the relevant documents and advise you of your options.

When you apply for a green card after an approved I-526 petition, you will be asked about your immigration history. I see it unlikely that 15 years after the 5-year prohibition ended, provided you have nothing else that would make you inadmissible, there would be a problem here. But yes, you will need to disclose this when applying for the green card, but the I-526 petition itself is just concerned with the project and source of funds.

If it was a false claim to U.S. citizenship, and it created a lifetime bar from ever getting a green card, and no waivers are available.

This question cannot be answered with certainty based on the information provided. If you were indeed barred only for 5 years and 20 years has passed, then you are likely admissible. However, you should seek a review of your file in order to determine whether you pleaded to fraud and/or willful misrepresentation in connection with seeking an immigration benefit. A person may be barred from admission for the rest of his or her life unless a waiver is granted. The I-526 process is lengthy and costly; I see no reason why you would embark upon it without confirming your admissibility.

If you made a false claim to U.S. citizenship after 1996, you are barred for life from immigrating.

If it is a false claim to citizenship after Oct. 30, 1996, there is no way for residency. If before, you may be able to obtain a waiver with the right qualifying relative.